I have a 20 speed road bike, and only use 10 of the gears - never get fast enough in traffic to get onto the big front ring. I have a fixed speed which still allows me to go fast but obviously requires a bit of effort up the hills. I have a 24 speed hybrid and again don't get onto the big ring, just use the 2 small rings.

FWIW my average speed over a 9.5 mile commute is around 14-15mph, max speed around 25-28mph and this is in heavy traffic with some minor hills and pretty poor road surface on both a hybrid and a road bike - haven't done it on my fixed speed!

I'd suggest a 1x9 for you - easier maintenance and some gear selection. Derailleurs don't require too much maintenance.