Heading to fork pretty soon. Is 15lb line too light? Don't really want to baby my line but also want to be able to cast well.

I use 20lb flouro for plastics or 30 lb braid for traps and spinner baits. I have had many big fish wrap me and break off around stumps with less than that. You may catch a few more fish with lighter line but you could always splice a 2-4 foot leader of lighter line to 20 or braid and get the same effect without losing the safety of heavy line. I remember one suicidal big fish that inhaled a lizard, headed for shallow water, and zig-zagged around stumps and stick ups until she had enough resistance to break the line. It was like she was running a milk route. i am sure she had done it before to others. All of this was visible in crystal clear shallow water.

"Big fish not only break your line, they break your heart" (Trilene Big Game commercial from the 80s)
I fish fork for big fish. I have friends that came with me and used 12 or 15 and get broke off at the speed of light from big fish. Then, they re-spool with fresh 20 after they lose the fish.
14 or 15 is good for deep diver crank baits in late spring and summer off humps and ledges. But for grass and timber, I go heavy.

20# for mono. Too many big fish to break your heart.