First off, why'd you promise yourself not to fall in love? I think that's a terrible idea. It's the same thing as eating bread and drinking water for every meal from now on. Boring.
Next, if you're attracted to someone, go for it. There's no reason to NOT go for it. Even a few rejections are better than being alone forever.
Anyway, your story about the pizza place made me think twice about "going for it". If he's one of those people who talks to you one minute then ignores you the next, I wouldn't consider that "relationship" material. As much as I believe in being completely open with your emotions with everyone (including this bass guy you're talking about), I think a sort of abandonment in communication is a huge impairment.
Another thing: If he leaves in 17 days, I'm not sure what effect your feelings will have on him. If you tell him how you feel, he won't stay for long. If you hold your feelings back, he leaves without knowing how you felt. It's your choice.
Also, I don't accept that personal belittlement of "he's friends with other pretty girls" stuff. Who cares? I haven't driven anyone wrong yet by saying there is no "He/she's too good for me because of such and such". Thinking someone's friends are rather fine-looking doesn't mean he can't be attracted to you.
Hope this helps.
I am homosexual. A lesbian, actually. If you have a problem with that, then it sucks for you. It's not your problem. It's not even a problem. I quite like it this way.