Where should I go this summer?

Where should I go this summer?

1. Europe.  I really like coming back to Europe for some weeks. But my visa to re-enter the US expires on June, 2nd. And I only finish school at mid-May and have to move out to a new apartment at late May. So this seems to be out of questions for me.  Next year, I promise. 

2. Vietnam. I want to come back once every year. But I don't like being in Vietnam in the summer, it's so hot. I prefer in the winter, where I can relax and enjoy eating and drinking in the year-ending atmosphere. Moreover, it may be complicated if I go in the summer while working as an assistant for some professor. And if I come back in the summer, I'll not be able to come back at Christmas.

3. United States. I don't know why but I don't feel really like traveling here in US.  Well, actually, there are certain reasons. First, it's expensive. Second, I don't have many friends in other US cities. Third, I don't have a car and don't know how to drive yet, which is an obstacle for traveling in this automobile-crazy nation. Fourth, I have a feeling that most of US cities are boring. Perhaps the natural sighseeing places are beautiful (Niagra Falls, Grand Canyon etc) but you need to go by car and with companions.

4. The only possible alternative left is Mexico or Canada, where I don't need a US visa to re-enter the US. But I know almost noone there and well, don't find these places very exciting to visit.

So where should I go in this summer? Perhaps some US cities, maybe going to the East Coast  again? There's a small chance that I'll come back to Vietnam in summer, perhaps for one month, but I'm not so sure about it. Time flies fast. It's almost a year since I went back to Vietnam last year.