There is a provision in the regs that allow ANG units to select UPT candidates before they actually graduate. Unfortunately, most have been burned so many times by selectees who promised "Oh I'll graduate next semester", and then slipped so much that the unit lost their UPT slot that year. You'll be hard pressed to find a unit that will select you without a degree unless you have massive political clout (governor's nephew, AG's daughter, something like that.)
Actually, a lot of units require political clout to be selected at all. I'm all for the advantages of Guard/Reserve, but the competition for their UPT slots are FIERCE. Usually 10-20 qualified applicants per selection. You have a much better chance overall with a ROTC unit, or even an OTS slot.