Okay, here's a better way to put my point: slang has its place, and in some cases can even be more vivid at getting a particular thought/emotion across than can regular language; but sometimes wigger/street slang, or any slang, becomes a crutch to the point where one's just repeating a meaningless catchphrase. Think about it: when some rapper ends every sentence with "Know what I'm sayin . . ." or "Keepin' it real" or "Represent!", what does that communicate, or add to what he said before that phrase? Nothing -- it's just a placeholder or verbal tic (you could think of a lot of analogies from other slang, such as the Valley Girl overuse of "totally" and "like"). Your goal with your girl is to be creative and to communicate exactly what you want to communicate, when you want to. Now admittedly, it's possible to overanalyze these things, but speaking to (and especially e-mailing and SMSing) a girl is a time to think closely about what you're saying, choose your words, and make a good impression (which doeesn't mean you have to use fancy language; just means you have to think it through). It's hard to do this in "real time," and I know that using slang phrases or cliches is one way to make it easier (heck, businessmen use goofy business jargon in meetings for the same reason) but I'm just suggesting that it's worth paying a little more attention to trying to select your words and match your thoughts.
It also worries me that you're trying to type as fast as possible. I hope that's not true with the ladies. First, it seems overeager (that's why I'm not a big fan of SMS -- you either have to give it your constant attention or else the conversation gets all garbled/overlaps; but paying that much attention, and typing that fast, makes it look like you've got nothing better to do; plus, it's kind of hard to end an SMS chat gracefully). Again, I think your goal is to say something that looks casual but actually has some thought put into it -- I know a guy who spends ten minutes or so writing a 2 sentence e-mail to a girl he's after -- but he only e-mails her every now and then, and his two sentence e-mail (despite the thought he puts into it) sounds super-casual, avoids giving any wrong/weak impressions, etc., because he's thought through what her reaction to each particular phrase might be. Anyway, that's my $0.02 -- if you want to use your own group's slang, fine; but even then, use it to enhance your meaning (not hide it behind hastily strung together cliches -- not that you're necessarily doing that all the time, just that it's a danger of combining quick writing with stock phrases).
Now to answer your question. You haven't really told us enough about your background with this girl, how you know her, etc. But on the chance you made a bad impression with the hang-up, etc. on Mon., why not wait a bit? If she really is liking you, she'll still be liking you Fri.
