I went with my wife January 20 - 22. I had originally booked an award stay at the Hyatt, but after some bad reviews and the fact it's not on the beach I decided to look elsewhere. We were able to book the
Park Royal Hotel with an all inclusive rate of $184/night through Orbitz plus $14 in tax/fees, so it came out to under $200/night all-in. The hotel is on the other side of the bay from the rest of the action, but overall we really enjoyed it. The rooms were nice, though very sparse (no alarm clocks!), but they actually had really nice TV's (Phillips flat tube TV's).
The food was fine I thought, considering it's all inclusive, and the alcoholic beverages did their job. For the total price, and considering we enjoyed just laying on the beach and around the pool, it was great. Most of the complaints I read online concerning this hotel related to the variety of food, but as long as you're not there for a week or more, it shouldn't be too bad.
I decided to just rent a car from Hertz since it was only $65 total for two days. I reserved the cheapest car they had with an automatic, got a Dodge Neon with 70,000+ kilometers, but it was fine, though it bottomed out a few times on the bigger speed bumps and other road anamolies around the city. If you rent a car, make sure to check the gas gauge, they don't rent them with full tanks, and in our case the tank was very empty when we picked it up! Valet parking at our hotel was only 30 pesos a day.
As for getting pesos ... I'm not sure I'd bother ... either you can use your credit card to pay for stuff or just pay with USD at a 10-1 rate, which while not quite as good as you may get elsewhere, is certainly convenient. The gas station, airport bar, hotel gift shop, and flea market merchants we dealt with all gladly accepted US dollars, and they would provide change in pesos. If anything I would just bring lots of fives and ones so as to avoid getting stuck with many pesos at the end of the trip.