Just got back - had no problems whatsoever and a wonderful time. Be aware if you want to visit Calakmul that it is a bit of a mess and has become quite expensive - about $25/person - you have to pay to drive thru ejidal lands, then at the museum for the museum and the ride the last 20 miles in a "cattle car" the kind of vehicle you might see in a safari park - a truck with seats in the back pulling a trailer full of seats, then again once you reach the ruins. They are apparently trying to restrict access somewhat to the site - and the ride in the cattle car is not pleasant and about 1 hr long going and coming. If you get carsick, try to go in one of the few vans, but you will likely have to take what you can get. The site is a good site to visit, although the hassle factor almost makes it not worth it. Get there early (like 7 am or earlier, I think they open at 6:30) to sign up for a slot - I was there at 8 am and couldn't get a slot until noon. Then be sure and show up 1/2 hour or so early for your time slot, since the vehicle may be leaving early - we ended up leaving at 11:30, not noon. The site is very large with a lot of walking. I felt rushed due to needing to be able to get a ride back out. Hopefully they will work out a better way of dealing with what does appear to be a rather dangerous road the last 20 miles - very narrow, winding etc., but at the moment the solution is VERY unsatisfactory.