Elizabeth, I live in Boston too and I can tell you, the car alarms are a little more than a minor annoyance when I hear them. I mean when a stiff wind blows half a dozen cars start blaring. This "overalarming" or crying "wolf" too much has effectively diminished the effect of a car alarm to nil. If someone wants your car they will take it alarm or not. Save your money in my opinion. Lojack I've heard is also very defeatable by driving the car into a shielded bunker for example or into an area that is not covered by receivers. You are correct in pointing out that Volvos are not high theft material (lucky for us), so just take heart in that. Also, from my own experience, if you get a car that blends in well colorwise, don't wash it more than average, don't put any flashy accessories on it and in general don't make it stand out from the crowd, the chances of it being stolen or broken into are greatly reduced. I usually keep nothing visible in the car. If you were to look inside my car you would only see a child booster seat, a road atlas in the back pocket of the front passenger seat and a cheapo pencil-style tire gauge in the door pocket. Not very interesting to break into the car like that.

Good luck and enjoy!