I went with http://www.cesiak.org/contactus.htm
in December, 2010. I was (and am) still a newby and had never casted such a heavy line but the guide was very patient. Even snapped a Sage rod in half 30 minutes in to the day!
We fished in a huge salt water bay in the Sian Kaan bio-reserve near Tulum. We saw lots of bonefish but I could not cast longer than 15-20' and you need to be able to get it out at least 40-50' to reach them. The guide saw where the day was headed and took us to a spot with some other less spooky fish so we didn't get totally skunked.
Seems like the price was around $400-500 for 2 people. We actually had 3 (me, brother and wife). Had planned to fish 2 at a time till genius here broke our second rod.
They provided drinks and lunch but I'd recommend bringing your own snacks. Call me crazy, but a mexican ham sandwich sitting in the hot sun for 4+ hours wasn't the best idea. May be a bit of a drive from Cancun but I would recommend a night in Tulum - very cool little town.
I'd go back, once I can cast a bit better!