I stupidly poured about 1/2 quart of oil in my radiator (cap screwup). I'm sure I need to get this backflushed. But can I drive it to a mechanic or do I need to have it towed? 2003 BMW X5.

I would drain it and flush it where it sits, or have it towed.

I would open the drain and let the radiator empty. Then I would flush with distilled water and let it drain. Next, I would add a radiator flush to distilled water and drive the car for 20 minutes. I would drain this and then add a 50/50 mixture of antifreeze and distilled water.

Txgreasemonkey has offered sage advice, for someone who is able, and wishes to cure the problem themselves. But, for the person who only chooses the options of a tow-truck, or a drive to the garage, I would drive the car. All that I can see resulting from a short drive with some oil in the radiator is a rather nasty emulsion of oil and water, with some extra lubrication to the water pump. Since I have never experienced this problem, I might have overlooked something. Let me know.

I stupidly poured about 1/2 quart of oil in my radiator (cap screwup). I'm sure I need to get this backflushed. But can I drive it to a mechanic or do I need to have it towed? 2003 BMW X5.
Yes you can drive it. I'd leave it in. It'll lubricate the water pump.

I don't think a short drive to a repair shop would make any difference just be sure they
Do a thorough flush of the rad and the block with all drain points open in the block and
Running clear if you don't want to do it yourself at home.
It may be necessary to repeat after a few hundred miles if oil globs are still seen in the radiator.

I did this recently on a mini van, but I did it with trans fluid. (same color as the coolant) and wasn't paying attention to my containers. I had to flush twice, the watch it run to full warm up and let the coolant spill over the top of the radiator because oil will come to the top. The oil will start to soften the rubber hoses if left in there so get all you can out.