It might be worth researching the Texan coast (e.g. South Padre Island - a bit like Benidorm but i'm sure there are better options that where my college friends went on "Spring Break")...

edit: I've now been assured that South Padre Island, Lake Havisu (AZ) and all the other favoured "Spring Break" locations are fine - any time except the two weeks in march they are filled with uni students on the lash.

IAH is a relatively painless port of entry and CO has two daily non stops from LHR with connections right the way down the coast (and into Mexico if this appeals)