If they get the planes they can train in a lot of countries, which have offered training facilities.
The main uses of F-16s in Ukraine as I see it
1. As a CAP, covering several regions, looking to shoot down cruise missiles, to be a more flexible extension of the SAM system. The F16 should be good at this with its radar and AMRAAMs. The Ukrainians are running low on S300’s and probably want to reserve them for manned aircraft. There is no shortage of AMRAAMs.
2. Pop up launch of SDB or JDAM. This is something that the Ukrainians are already doing some of, but the F16s should be better at it. https://en.wikipedia.org/wiki/Toss_bombing
3. Should the Russians get inspired to risk losses and commit a large strike package into Ukrainian airspace, the F16’s can likewise be surged to oppose it, much better than the Mig 29s. They have much better radars and missiles. This is insurance, just in case the Russians change their behavior.
I doubt very much that Ukraine intends to commit the F16s into the Russian Air defense zone.
Any way you slice it, the uke pilots have less chance of getting meaningful hours to be able to use the ‘system’. American pilots flight hours are already too low.
Train the ukes outside of Ukraine, nice way to extend a war that won’t be won.