Is South Padre Island Safe for Spring Break Travel?

It should be. It is part of the United States.

For the most part; but don't be naive about the situation down south; it's a LOT worse than people realize. Look at the incident at Lake Falcon- a couple on jet ski's were chased and shot at by drug cartels on boat, killing the husband.. they then took his body and never got it back. The appointed lead investigator of the incident was beheaded shortly after that, case closed.. just be smart