All kidding aside; this is seriously good advice. The sub-tropical sun down there will fry you, and especially your kids, in such a short time you won't believe it, even on cloudy days. The effects will last a lifetime. Most of the time I spent down there was long before the days of sunscreen and my shoulders are a mess.
If you don't want to spend your golden years being periodically skinned alive by your dermatologist, slather on the strongest SPF goop you can find every time you go out. Big hats and SPF shirts are a good idea too.
WTF you think will happen if you walk around shirtless on a Montana prairie in mid-July?
Catch a fugkin' cold?