Avoid Edgewood and Aberdeen, regardless of what your realtor tells you. Joppa and Havre de Grace can be good or bad, but you have to choose carefully, both have problem areas. Grab lunch or take a walk in the area you're considering on a weekday and a Saturday or Sunday, don't just do a drive-by.
The general rule is the farther North of I95 you are, the better but it will also be more expensive. Try to get a place with natural gas, BGE is screwing everyone over on electricity rates and you'll need to use a lot more heat here vs NM.
If you're going to APG South, Rt 24 is a zoo in the mornings and afternoons, 152 is a disaster in the evening. For the North side, 22 is pretty easy once you get above I95, 543 is a bit worse since its the first I95 exit after Rt 24.