Can you get treated for a std before lab results come back?

Yes: It's the physician's judgement as to how likely infection is, if so what the likely bug is, and the best antibiotic for coverage. If I had an obvious chancre or had a urethral discharge with gram positive cocci, I'd be treated for syphilis or gonorrhea respectively. If I just had some irritation and suspected it was the jalepinos, I'd take no Rx & wait in a culture in the unlikely event it's bugs.