Ask 'em.... Of course they (or anyone else) will only quote maximum possible speed, which is determined primarily (in the case of DSL) by your distance to a central office (switching station), then line condition and a few other lesser things.
I would ask:
1) How far am I from the CO (Central Office) and YES, they can tell you that.
2) What average speeds you should expect.
They OWE you those answers.
You can then check your speeds by going to
http://dslreports.com and find their speed tests (they aren't 100% accurate, but close enough)
here is a link:
http://www.dslreports.com/stest?loc=97
(that is a test to a server in Cali, so should be pretty accurate for you.
Here are the results of my test ( using a Cali server, pretty damn good) for reference:
http://www.dslreports.com/speedtest...a9a85d60890;3.0;www.dslreports.com/1095395052
This is my 49/mth cable connection, granted not prime time on the internet. It would be even faster at say 3 AM. Overall internet traffic can slow you down regardless of how fast your connection "can" be.
Tell SBC you want a connection like that and see what they want to charge ya :p