My first composition for E Piano, Congas, and Vibraphone

I'm an amateur in many senses of the word—I have never composed in a professional or academic setting and have only begun learning some things about music theory this summer. I made this piece a few days ago and it's my longest composition, though still below two minutes long.

I think it's a very good job if you started study una a few weeks ago. It's nice the contemporary language you use here. For me the conga is the "melodic" instrument... 

This is actually really cool. The harmonies (intentional or not) are pretty well done.
For me, the piece loses steam after the first whole note a little bit; it doesn't have the same energy, even though the harmonies still remain pretty cool. It would have been a really good time to vary the structure a little bit after a bit of pause (variety is the spice of life and all that).
A lot of notational issues here;  be careful about your layers and always make sure to move your rests that the layers don't inhabit. In addition, make sure you use your dotted rhythms correctly. A lot of the time you should be using ties to make the beat of 4/4 as obvious as possible (correct beaming). If that wasn't your goal, then you need to switch your time signature. There aren't a lot of things that are strictly "right and wrong" about music, but this is definitely one of them.
I would really suggest having the congas be on a staff rather than a staff line as to differentiate your types of strokes a little bit better.
Good job, and keep it up.