Living in the Baltimore area

Hi there,
I think all the main points have been covered, but I'll add my thoughts...

Mountain biking: Yes, many opportunities, and if you're willing to travel an hour or so to Prince George's or northern/western Montgomery County you'll find some awesome places. Check out Patuxent State Park (Avalon area, and others) for closer to Baltimore. Haven't done much mountain biking lately, so that's where my knowledge ends.

Road biking: Only familiar with north/west of the city. Beautiful rolling hills/rural roads in Butler and nearby. There's even a cycling shop/cafe where rides start and coffee is bought in the middle of that area (Veloccino). Paved paths as well that go from Baltimore to Annapolis. The DC area has a ton too...from the Maryland burbs all the way around the DC beltway, into the city along the rivers/watershed, through some awesome parks (Rock Creek Park), and once you're in the city, the world's your oyster. DC has been doing a lot for cyclists lately (relatively speaking) so there are dedicated lanes, sometimes even separated from vehicular traffic. Also, you can basically ride along the C&O Canal/Potomac River from MD down to Mount Vernon on dedicated paved paths.

Living/Commuting:
Sounds like you've settled on being north of the city, but I'll say that commuting from the south (Columbia was mentioned) from I-95 is not too bad. The beltway can be miserable (honestly all of it can be) but it's certainly doable. Another suburb with good schools, community vibes, and charm is Catonsville (bonus you're close to some good mountain biking) which is directly west of town and also Ellicott City, which I view as a blending of Columbia and Catonsville (charm + newer communities, retail). Since you mention public schools are important, these three cities/towns are all excellent for the most part.

Best of luck with whatever you decide to do!