A lot of this is going to depend on where you live. In my area, the cable service rocks and is much faster than the advertised speeds and also faster than the DSL at the same price point. Both DSL and cable here are reliable (Verizon and Cox), however you'll find others on the forum that will tell you their cable sucks and DSL rules -- all depends on the provider. I just set my sister up with DSL yesterday. She has sucky cable, but her AT&T/ Yahoo DSL, which is the $14.99 cheapo special, is nearly as fast as my work connection.
I know this kinda muddys your waters. You might want to checkout DSLreports.com or similar to get reviews on service in your region.
As far as having a phone number, my sister had to provide hers to get service, though I saw there was an option for "if you don't have an AT&T phone number" so there is probably a workaround.