Truthly you will save A couple$ buying it at Wally world.But do you want too tote it around allday,were at the resort you can buy it as needed.Plus it will have something Universal onit,kinda like A souvie.
Honestly..we bought ours at WalMart several years ago and bring them with us every year. The ones at Universal are glorified trash bags. I got nice ones at WalMart 2 adult and 2 kids sizes for about $12. It is a lot cheaper and they hold up very well! My kids both have SpongeBob ones! We were asked one year which Universal store did we get them...I just laughed and said WalMart!
Every time we go we always visit the dollar store and buy the poncho's made by Colman (the camping equipment company). They are $1 and we buy about 12 of them. They are disposable and can last more than one day. Plus they take up very little space and can put them in a back pocket.