I have Comcast with 3mbps and I stream just fine. Not sure if you would have a problem streaming multiple devices at a time. I can stream while the wife is surfing the web without problems.
Also the price for basic cable they told you is never what you pay. Are you using a box or two? DVR? Add in the FCC fee, local taxes, federal tax, and whatever other shit they can dream up to throw in there and your TV is a lot more than you thought it was going to be.
Just get an antenna if you need local channels. I use old bunny ears from a TV I had in the early 90's. Great HD signal in town.
Oh, and buy your own modem. That was $8 a month here. Bought one for $50 or so.