It would not be my first pick in Port Isabel. Many do enjoy the people in
Park Center. If you're lucky you might get a site on the canal. Another park is
Long Island. It is an owner park that has a rental pool.
In a very crude analogy you can say Port Isabel is South Padre Island's poor cousin. When you cross the causeway the rent goes up.
Only two parks are on the Island, a county park and a KOA. The best thing about the county park is the people and the affordability during the coldest months ($500 vs $1300.) The KOA is a nice short term place or long term if budget isn't an issue.
Both parks have drawbacks that everyone overlooks if you enjoy being next to salt water and a safe place to be regardless of time or location. I guess crime doesn't like the idea that to get away, they only have one escape route to the mainland.