> who come from Europe for the summer and work in every service industry job imaginable in town

Do they have work visas for this, or are they abusing a travel visa? All the people I knew that did this were doing it illegally.

There is a "work and travel" program for students in Europe with valid visa and everything. I know lots of people who did that for a summer or two, it was an opportunity to see USA and also it was a great thing to list on their CV when getting a job back home.