admittedly i know little about the frame that you have but
1) does it have a 1 piece crank
2) does it weigh a ton
3) can you afford better
if yes to any of these questions then i would say no.
If you are going to be going 20 miles each way i would say get something that is at least niceish...
riding crap sucks... 20 miles is a long way and this should be fun.