Also carry some $20's and $5's. The 20's are for the handler and the 5's are for the line service etc.. The job market down there sucks so they hire lots of people for line, fueling, baggage handling etc. and a few dollars here and there goes a long way towards helping things go smoothly.
If you need prist then try to bring your own. Handler will tell you they have it, but sometimes you may end up "buying" some when you get there or they won't have it at all.
If you don't like Universal you can try ICCS. We always had good luck with them. It can all get expensive but also realize that everything else in Mexico is very cheap. Negra Modello for a buck!!