I lived in Gaithersburg the first 18 years of my life... It's not a bad area by any means, but Gaithersburg is also not small. There are parts that are nice and parts that are not so nice. For instance, Lakeforest Mall. Stay away from it.
One thing you may have to get used to is the people. One of the things I hated most about Montgomery County was how unfriendly and sterile everybody was. Soccer moms living in cookie cutter houses who flip the fuck out if you go 1 over in their neighborhood. Of course, once they're on the highways, they go about 20 over and are driving up exit ramps to get past you. God damn hypocrites.
Speaking of drivers, like creature said, 270 is a freaking disaster. What should be a 15 minute drive can turn into a 1 hour drive... and that's on a good day. I've sat in literally the same spot for 4 hours during rush hour before, although that was an anomaly. Learn the back roads as well as you can. You can trim off a very meaty portion of your commutes using them.
Takoma Park is the only gayish town in the area, but I really can't speak much on that... though I think I'd rather live in Dupont Circle.
Derwood (dry town - no liquor stores)
I only approve of Rockville and Bethesda, and Bethesda is only if you can afford it. Olney is about as much fun as plain white bread, Gaithersburg requires you to speak Spanish, and Germantown has an Applebees in the same shopping center as a Target and
a Walmart. Also, wtf is Derwood? I've never heard of that. Do you mean Damascus?
Really, anywhere near a red line metro stop is where you should be, as long as it's within your price range. If I were you, I'd focus on Rockville; it's a pretty cool city and it's relatively affordable.