For .20 - Plant them, what do you have to lose? Non heading means it will be loose leaf just like Black Simpson Lettuce (just wont make a head but will grow individually)
I don't think it's too late....at all. Planted my, in the garden, on January 20th and they are VERY little, due to the cold weather "holding them back".......but they ARE growing.
Bolt means go to seed. A lot will depend on what kind of weather temperature wise and sunshine wise there is between now and say May 15. Hot April, they will probably bolt. But I would still plant them. You will get something, but it takes a lot of greens to make a mess. Once greens bolt they tend to get a bitter taste to them. I sowed some mustard greens about 10 days ago so I am hoping they give me a few greens and some seeds as well! Good luck!