The more I think about it, the more I think it was bored teens. The immediate neighbors kids are all straight arrows, but there are a lot of teens in the neighborhood.

If a pro or pro-am for lack of better words wants in, there's nothing I can do to stop them. But I did come across a number of studies about burglary methods below and there seems to be a couple of noteworthy points.

1) Burglars prefer to be not visible from the street, but will enter from there
2) No preference between doors or windows for entry
3) Unlocked or open anything is a common way in.
4) Hinged entrances will be kicked or pried open
5) Sliding entrances will be rocked off the tracks
6) They don't like deadbolted doors
7) They really don't like double paned windows, but will break single paned windows on occasion. Double paned are probably noisy as all getout.
8) Dusk to dawn lighting is detrimental as it's helps them see what they're doing.

Keep your doors and windows locked (duh!), install anti-lift devices on all sliding entrances, install deadbolts with high security strike plates on hinged entrances, replace single pane windows with double pane (or install security film), and don't rely on stock window locks.

The Chula Vista Residential Burglary Reduction Project (largely blue collar community south of downtown San Diego)
http://www.popcenter.org/library/awards/goldstein/2001/01-12(F).pdf

State farm
http://www.statefarm.com/learning/be_safe/home/burglary/learning_besafe_athome_doorlocks.asp