My dd3 is exactly the same - I put a suit on her that buttons under her crotch and she can't undo it. She still gets changed a thousand times a day - but we have to do it so she keeps her nappy on!

My other kids have all been nudists, I just sort of let it go - they'll get dressed when they're cold I figure.

With going out to other places, I just try to keep them busy so they don't strip off LOL