Is it too late to plant tomato plants in pots on your back porch?

no it is not

that depends on your hardiness zone which you have not stated

Try cherry and grape tomatoes instead of full size tomatoes on your porch. You have to be careful planting full size tomatoes in pots because as they get large and heavy with fruit they can topple over in a strong wind/storm and the plants will break off--you may end up with nothing!

Hi Alice. I am not sure of your location. As long as you still have at least 2 months of growing season you should be fine.

Plant the tomato plants in the planters and put them under a grow light if you don't have a sunny area in which to set the pots. As soon as the last spring killing frost has passed, set the pots outside. This will give you a big headstart on getting ripe tomatoes. Be sure to keep them watered well but not soggy, and they'll repay you with lots of ripe tomatoes.