He will get it tuned much better than not tuning at all.
I tuned mine in a semi empty Lowe's home improvement parking lot.
The real thing is to make sure you aren't like up against a wall or light post or something. have the antenna free of obstructions...including someone that may be holding the SWR meter if you hook the meter up to the antenna side.
If you are trying to squeak every last fraction of a mile out of your set up, then sure, find the absolutely most flat remote place you can. Otherwise, even a few parking spots of emptiness should be decent enough