Hope you guys have a great time! Foursquare was super helpful, so don't be a slave to this list; definitely Foursquare your away around. But don't miss El Fogon and Los Hijos de la Tostada.
Beside the specific recommendations below, you should spend a lot of time just walking up and down 5th Avenue (Calle Quinta Avenida); it's pedestrians only and where most of the spots are. We found the whole area to be safe, so feel free to explore.
You might want to spend an afternoon visiting one of the cenotes (the partially underwater caves), too. They're really pretty to just swim around it. The one we went to was by Tulum, so pretty far from PdC, but I think there are a bunch near Playa del Carmen if you just look on tripadvisor. The hotel concierge can probably help too.
C-Grill: If you're feeling like just staying by the beach, the hotel breakfast was actually pretty great. Definitely pricier than other options, but worth it if you're in the mood to chill.
Madrez! Café If you're heading out for the day, stop in here for a quick bite to eat (either outside at one of their picnic tables, or to go). It's right across the street from the hotel. Decent coffee too. Meg really liked their breakfast sandwich.
El Fogon best tacos in the world. Super super cheap. We pigged out on tacos al pastor, tons of sides, guac, chips, margaritas, and it was like $30 with tip. Amazing. Please do not miss this place!
Los Hijos de la Tostada This place was probably the best raw seafood I've ever had. Tuna tostada was amazing. Great margaritas too. Coconut shrimp was also amazing. Nice atmosphere too—it's partially outside. It's a bit of a walk (approx 18 mins, so not that bad), but we borrowed bikes from the hotel to get there for free and had a nice time. There are bike lanes and traffic is slow, so biking's pretty easy. Another do-not-miss.
Carboncitos Sort of cheesy Mexican restaurant like what you'd find in the states, but it was good food and really fun. The waiters balance your drink on their head to bring it to you lol.
Patio 8 Touristy spot, but open to the sidewalk in a busy stretch so a great place to grab a cocktail and people watch. Dinner was good there, but pricey.
La Cochi-loka If you're out late, stop by here on the way home and grab some cheap tacos. It's a tiny place with just a counter facing the street and a bunch of sauces, but man they were delicious!
Club De La Cerveza Really great beer bar right on 5th ave. Good place to take a break and crab a craft beer if you've been walking around shopping for too long.
Carmen Beer Co If you end up renting a car and have a rainy day, this is a fun brewery with nice staff to spend some time. Wouldn't go out of my way for it otherwise though; it's in a strip mall, and pretty small.
Hotel Bar The hotel bar was also pretty good. Make sure you do the free tequila tasting. :)
Walmart If you end up renting a car, park it here for free. It's only about a 5-10 min walk from hotel, and you can leave it there as long as you want (overnight is no problem). Also good if you need any supplies.
Playa Xpu-Ha We didn't make it there, but the hotel bartender said this is a beautiful beach about 10 mins away by car; might be worth it if you're looking to find something more peaceful and quiet.
Pesos are about 20:1, so a quick way to convert is get rid of the last digit and cut it in half. For example, to convert 120 pesos to dollars, take off a zero (12), and cut it in half: about $6.
If you get pulled over for something, or run into a police roadblock, don't worry; the police in that area aren't corrupt and it'll be fine.
It is Mexico, so things will be a little sketchy at times. We didn't experience anything unsafe, just a little annoying.
For example, when we got gas, they offered to "check our oil levels" etc for extra money, and hope you won't understand and just say yes, and then they tell you you owe them an extra 5 bucks. Make sure you say no and you'll be fine. They also tried to shortchange at the gas station, but I noticed and said something and he apologized and gave me the money. Apparently it's a fairly common scam:
Be careful when you’re filling your car at the gas station. Unlike in the US, you won’t get out of your car in Mexico as they have workers filling your car for you. You’ll also pay them instead of the machine, so have cash with you. What should you pay attention to?
Make sure that you check the gas meter before the attendant starts filling your tank. Some attendants tend to not reset the meter, making you pay more than you’re getting. Since this scam has become well known, many honest attendants will point at zeros to you before they start pumping.
Another thing to avoid is to make sure which bills are you handing to your attendant. People tend to swap bills, claiming you gave them let’s say 50 Pesos note instead of 500 Pesos note, so make sure to pay attention. If this happens to you, be firm and tell them NO. Most people will hand you back your change after you make a scene.
Another example: at the car rental place, the guy behind the counter told me if I tipped him $20, he'd give me their nicest car for the price of the cheap car. It was actually a great deal but I didn't take it because I wanted a manual lol!
The other "scam" we ran into was someone coming by to take your picture while you're at dinner. We thought it was just another waiter doing it to put our picture on the wall for advertising, but after he took it he printed it out and tried to sell it to us for $20.
For car rental, we used Alamo booked through Expedia, picked up at the airport. We didn't have any problems, but you should know they'll force you to pay about $20/day on top of what you paid to book it (which was probably like 2 bucks a day) for car insurance. This isn't a scam, it's Mexican law, but we saw a bunch of people freak out at the rental place thinking they were being taken advantage of.