You may hold as many acceptance as you want until May 15th (after then you may only hold one). So, yes ... send in your deposit to hold your UCHSC spot (congratulations!!) and then you can wait until May 15th to hear from your first choice.
it is proper, according the staff at my school (and it seems reasonable) to withdraw from all schools whcih you know you would not be interested in. Also, you should only hold one acceptance at a time unless you are truly conflicted, seriously considering multiple schools, or waiting on financial aid information. Basically, try to avoid wasting the time of schools you know youre not interested in.
Were you accepted to CU? Woo hoo! Congratulations! Are you going to try to make it to the April 22 get together? I'd like to, but they changed it to the same weekend that UM is having their 2nd look weekend.