I would not bother with doing a PADI course in Argentina -- you'll do your practice in a pool, your "dives" in the river and then maybe a deep dive at a crapola quarry or something. You're the one going to Central America, no? Do your PADI in the Bay Islands, Belize, or Mexico. You'll be thrilled that you did. Not sure how diving is in the CR or Panama. Mexico I've dived a bunch of times, it's decent. There were quite a few hurricanes that passed through in the past few years so unfortunately a lot of the corals have been damaged around Cozumel, but for intro diving you'll like it, not too many heavy currents to deal with, good viz. Most life is between the 5 - 15m depth so you don't really have to do your advanced unless you're like me and want to do deep dives to 50m for some silly reason. Advanced will let you do wreck dives though which are great fun, as long as you don't have problems with claustrophobia.