It it possible. Of course it is. There are still a lot of 56k'ers out there. I myself was until 3 weeks ago when I finally got DSL. I played CS for 2 years with a 56k modem, and before that numerous other MP games. It will be harder and you will be at a disadvantage but you will still be able to have a good time if you find a good server that doesn't lag too much. If there happens to be DSL or cable in your area and you just haven't gotten it yet you really need to try to get it because it is definitely worth it. It is usually only about $20 more a month than a regular dial up service. If your parents won't let you get it try to work a deal out with them. Like with my parents I now pay the $20 difference each month (and I had to keep my job that I was going to quit
) But yea it will work, but you'd have a better time with broadband if it is available.
ALSO, look at it this way. If you aren't able to get broadband you will be building your skills because you will be at a disadvantage and when you do get it, you will be totally kicking @$$, just like I am in CS...well, not really, but you understand what I'm sayin right