I did Corona>San Clemente a couple of weeks ago and did the first half on the SART. I agree the homeless camps by Honda Center have swelled and is nearing critical mass. (I'm pretty sure they weren't tailgating for the playoffs)
While I can't exactly say I felt unsafe per se, I can say that I was definitely creeped out. On top of that, it's also not the most sanitary place I've ever seen in my life. So while I wasn't really afraid of getting bike jacked or anything, I was definitely happy getting past there.
There's no easy answer for this. Not to be harsh, but the SART is ours -- not theirs. It's a riding path and was not constructed as transient housing. So should something be done? Sure. Yet, they're still human beings and many of them are dealing with severe mental illness, addiction, or both (which, regardless of your political leanings... is not an easy thing to get help with in our society). It sounds easy to say "get 'em out of there", but it's way more complicated than that. Wherever they go, that place won't want them either.
As cyclists, we have a right to feel safe on our riding path and shouldn't feel like we have to exit our path. If you feel legit unsafe on the SART, this is what "phone calls to your lawmakers" is for. I'll likely be doing this myself, and I suggest you do too.