For those that want to come into the US for training there are several schools which have loaner guns or even require you to shoot their guns. If you’re going to bring you’re own weapons in – first check with CBP on line – I would recommend flying in to Los Vegas, Houston or Miami. Those are all international airports in gun friendly states. Avoid the north east and California if at all possible.
Cover vs. Concealment. Remember during the first few days, the walls of a normal residence are concealment (if you know that someone is using a window to fire/observe) and you can shoot at them through the walls. Cinder block, brick, and concrete structures I wouldn’t waste my ammo (unless you have 7.62 US black tips), but a building with siding or stucko I would be willing to fire IF needed. If you are useing 5.56/.223, you will want a supply of the military green tip rounds to punch through walls; if you only have 55 grn hollow points, save your ammo. After the first few days people will have everything they can lay their hands on to give them better cover.