The easiest solution is if they have WiFi available where you are staying. If that's not the case, hopefully you have the iPad 3G which can use the cell phone networks.
Assuming you have a 3G, you can either pay AT&T a lot of money for a little data (e.g. $25 for 20MB of data). Or you can buy a much more reasonable plan from a local carrier and swap in their SIM card.
I had a great experience when I was in Mexico over Christmas. I went into the main Telcel store in Puerto Vallarta and was informed that their iPad plan was free for the first month and and they also had a promotion on which increased the monthly allotment from 3GB to 6GB. Since I was just there for 2 weeks, I paid nothing and they even gave me the SIM.
I used MyWi to share the connection with my laptop and my sister's iPad and laptop. I used about 2GB, which would have been stupidly expensive through AT&T.