Air-Con Security

[treebeardy.livejournal.com]

Long time reader/first time poster.
Summer's coming and we're debating whether or not to get an A/C unit. We live on the first floor so we're hesitant because of the security issue. We can't decide if it's a good or a bad thing that we're living on a well-lit busy street (highland ave).
It's our first summer in Somerville so we're not sure if we can handle the heat. Surely being on the first floor is an advantage for the natural heat flow of the house.

Any good advice out there?
cheers