It's a crapshoot - some actually feed on mites and other harmful insects; but many more feed on pollen (ok, that's not a bad thing) and the chloroplasts of the plant. Some actually pollinate plants through their actions.
But many carry plant diseases, some of which can act rather quickly. According to the Wikipedia article on thrips, they are known to carry over 20 viruses that infect plants.
If you had more time, I'd suggest that you plant at least one Mexican marigold in the same pot (up-potting if you felt it to be necessary). Might still help, I don't know. I believe that pymethrin(sp?) is effective, but do not know how quickly the MMs release it into the soil.
Contact Sierra Natural Science and Liquid Ladybug (both are site
sponsors) to ask if their products are useful against thrips.
Perhaps some yellow/blue/white sticky-traps on the soil's surface? I don't know whether or not they go to ground in order to lay eggs (I suspect not but am unsure).
There are a few predators, but I don't know how helpful they would be in an open environment (since it is quite likely that they'd find all the thrips they wanted to eat nearby).
Some insecticides are especially helpful, but I have not looked into the impact on people consuming crops that have been so treated.
Maybe the addition of a silica product such as General Hydroponics' Rare Earth to your soil would help?
I always considered thrips to be potentially devastating. Hopefully, they will only be an annoyance to your plant.