I don't think it's a matter of safe to drive, if the compressor is off, your lines will be open. I would leave the A/C and temperature regulator off if you intend to drive. I didn't get it rebuild, I did an "échange standard". This means they send you an overhauled one and you send your core back. This means no downtime of the car, and no problems with A/C lines being open for a while. I know you will top your A/C lines, but can you be 100% sure they're sealed?