I am a guest at the Hilton Hotel Cocoa beach, and they have free wifi. Is it safe to use it?

[DunbarPappy®ϟϟ]

A few things to consider:
"Open" (no encryption) means ANYONE within 100' or so can 'sniff' your traffic.

High value sites commonly employ SSL connection, which means traffic would be encrypted right to and from your computer. (SSL has 'https' on the address prefix). So this type of traffic could not be seen by 'sniffing'...it's all just noise to them.

Conditional aspects to the above:
If you must 'agree' to the Terms and Conditions of the WiFi provider, make certain to understand if they will be issuing (from the router to your computer) a "Certificate". If yes, then the router can (may?) be doing any encryption when you connect to high value sites, and in theory your traffic can go to that> be decrypted> logged> re-encrypted> launched to the destination. That's very bad.

It's all dependent on how the WiFi is set up.
When you do connect to a hi value site, make sure to examine, before conducting any business, the pedigree of the Certificate and determine if it's from the site you are on; or if there is an interloper (that WiFi router) between you and the site. If that's the case, I would not trust any part of it...strictly casual browsing only.
If you've already agreed to any terms, check the Certificate and see what's up.