Toulouse truely sucks for accommodation. It's crappy and expensive. I stayed at Residence Jolimont - http://www.hihostels.com/dba/hostels-Toulouse---R%C3%A9sidence-Jolimont-020185.en.htm?himap=Y#book
It is a HI hostel and it is close to the train station. But it's very impersonal with roughly 200 beds in the place. It felt more like a boarding school to me. Plus, one of the guys in my room had something stolen by another guy who was in the room for all of a few hours. Fortunately, a couple of days later I got an offer to stay with a friend.
I'd definitely recommend signing up to Couchsurfing.org and Globalfreeloaders.com. You'll get a far better feel for the place if you have someone with you that can show you around a little and help you out if and when the language becomes an issue. almost 7 years ago