I just came back from Mexico and got one day's fishing in at Pesca Maya Lodge on Ascension Bay.
I was staying about 10 minutes outh of Playa de Carmen. I'm a newbie bonefisher so I didn't consider the DIY option. Instead I dished out the big bucks and had a driver pick me up early in the morning for the 2 hour drive to the lodge near Punta Allen.
The day was windy so we had to fish in the back lagoons and flats. Saw quite a few tailing bones but I only managed to land two. The guide, Luis, was great and I learned a lot about spotting cruising and tailing fish.
Ascension Bay itself is not DIY water. On the way to bay we went over the Boca Paila bridge where some people have mentioned DIY. I'm not familiar with salt lagoons/flats and tides so I wouldn't consider doing it myself at this time.
I did wake up really early to fish the beach at my resort (Barcelo Maya). I spooked a few tailing bones on the south side of the beach. Never got a cast at them. Also walked into the neighbouring resort to the south and fished off the rocks in the deeper water and landed a few fish...lost something bigger.
Hope that helps,