running 31s spoa with megacrawlers, rear locked. I am wondering how locking the front will affect turning/// I want to keep my turning radius. not skilled enough to add power steering...

It will kill your turning radius in 4WD.  Won't matter if the hubs are unlocked.  So, whats more important, being able to turn, or climb anything in your way easily...lol

So, what your saying is I should spend lots of money on a limited slip diff? do those help much?

if you get a selectable locker for the front (like an ARB), and only lock it in when you need it, it will work fine

mine make caddy turns in the loose graveland dirt.will selectable rear brake lockout allow for tighter turn with limited slip in rear?

or raid a tracker, sidekick for its powersteering, and do the powersteering conversion in the sammy, friend of mine just did it, works nice with lockers front and rear on 31's

It's not like you WON'T be able to turn, you'll just have to get used to 5 point turns and all.  I'm locked F/R and would rather sacrifice the tight turning radius for the advantages off road.
I also have power steering, and while I'm still doing 5 point turns, I do them with one finger 

I am very tempted to lock the front. I can't afford airlockers... So, instead of trips to the gym Ican maybe just drive aroung the block parking everywhere for a work out...

Pretty much everyone I know who has their locker installed correctly has power steering.