First can a guy get a 2.5 inch Steel pipe bent to a 90 degree without weakening it? And where would a guy take it to get it done?

A few factors would come into play. The first question is what is the size of the pipe and intended application

A cold bend will allow the metal to keep it structural integrity. Also depending on the application and 90 degree elbow can be welding in place instead of a bend

With a thin thickness like that Id find an exhaust and muffler shop and see if they can put it in a pipe bender

This but is there a particular radius you need the 90 bent or do you just need a 90 degree turn and don’t care if it’s a sweeping bend or a normal short radius 90 degree welding elbow. In today’s world the muffler shops are all using inside mandrels on their benders so they can do a nice job without the inside bend wrinkles on thin-wall piping.

Try a muffler shop.

Sounds like you need a welding elbow which would be 2-3/8” OD. If you need a longer radius, a conduit bender might be your answer.

If you're good, and it's not structural...you can take pipe of the same size, and cut a great many pie shape wedges, and fit them in a 90, but like said not good for structure just purdiness.

When you say 2 1/2 pipe, it opens a can of worms. 2 1/2 pipe is 2.9 inches od winth an id of just over 2 inches. That is a standard pipe size. If it measures 2 1/2 inches od, it is a tubing and can be anything for wall and Id. A muffler shop makes crimp bends, and are no where near as strong as a good radius bend. Pipe bending is an art, and takes the right tools to make the bends and keep the size of the material consistant.

Only two ways to bend it, one with a mandrel bender, pipe place or maybe a muffler shop may help you , or two with cutting it and welding in a elbow !

One last way has been suggested but you better be a good welder and that would be sectioning it
out then welding it back together, a lot more work and with light duty pipe, one should be a very good welder !

I came back to this after giving it some more thought, one more way you can do this at home depending on leg sizes
sounds corny but is doable, I have done it before with smaller legs because it was a home job.

Get you some sand will need a good amount find where you bend is needed and mark it plus a foot or two further
make another mark, fill these area from mar to mark with the sand, block up your pipe and make it so one leg will not
move anchored very well, now heat up where the bend is to be to a cherry red color all the way around, will take a bit of
time as the sand will absorb some of the heat, when it gets to the red color have some one start putting pressure
on the loose leg in you L shape you need until you reach it, block it and let it cool down. don't go fast but go steady
keeping heat where needed while moving it. once you happy, let it be, don't throw water on it just let cool on its own

Yes a lot of effort but the cheapest way do a elbow 90 on thin pipe in one piece !!

Good Luck

I think a muffler shop is good advice or finding someone in the trades that has a hydraulic conduit bender

I bend ridged schedule 40 pipe in my hydraulic pipe bender .
I can bend 90's , in up to 4 inch pipe - one shot ..
Find an electrical contractor in your area ..