Caulker is kinda a must-do since you're going to be in A/C for 2 months. It's the cheapest different place to get to and has a more laid back vibe, a little rasta -one love, one heart.
It's less expensive and less busy than SP so spend a few days once in awhile there to dry out after SP party binges. I think you're going to love it at both places and hope you do Canada proud.
As for security, remember the buddy system -3 girls are a force to be respected,keep the sisterhood together and walk whenever and wherever you wish in SP.

Have a blast, Joe from Toronto