There is plenty of other cool things to do than WW boating - check out the Trip Reports on the PPCS site which shows more than just WW. Falmouth... a very upscale location which would put you outside of the urban area of the city, but very close to it. The traffic is nowhere like DC and Boston - just the usual bottlenecks during the a.m. and p.m. commute. Your commute seems a very quick one - you'd get on the 295 and head south until you take one of 3 or 4 exits which will take you to the mall. 15 minutes sounds about right. Since it doesn't sound like you are thinking apartments, any of the locations around Portland are good. But if you are going in-town, I'd recommend the West End or Woodfords or Brighton St, as that's where most professionals are. As is usually true on the river, there are some places where you do not want to go :)
By June, the group usually have II-III runs on the Dead River - think 16 miles of continuous whitewater, so you will never get tired of it even after 100 runs. When people want to get home earlier on Sunday, some just do the lower half of the Kennebec which has a couple of III then II then swiftwater all the way to the Forks. June is bug season though, and it usually abates by the 2nd week of July.