2011 13inch MBP - Can I use 2 external displays - one with MINI DVI and one with Thunderbolt?
Duplicate question, see: Can I have multiple monitors on my MacBook Pro (Early 2011)?

Any 2011 MacBook Pro model will support Thunderbolt. You can daisy-chain 2 Thunderbolt displays. You can also connect one mini DisplayPort monitor to the end of a Thunderbolt chain and connect your Mac to your Thunderbolt Display.
A non-Thunderbolt solution if you don't have a Thunderbolt Mac: a DisplayLink-style USB to DVI display adapter.