Perhaps you might want to offer to come to a class and speak about entrepreneurship, programming and startups. Find a way to give first, and then at the end let them play with/use your app.

You can't go wrong if you are offering more than you are asking for.

Also, research has shown that you can get 80% of the information that you need from User testing with just 5 users. You might be able to get a lot more done with less people than you suspect.