Amadio,
We haven’t had any problems w/ thrips here (that I’ve been able to notice). I think thrips occur in more dry weather climates.
I’m sure Fruitnut has good advice because growing conditions are similar to yours. I would only add that if I were trying to control thrips w/ a Spinosyn class insecticide, I would go w/ Spintoram (i.e. Delegate). It is the synthetic counterpart of the organic compound Spinosad (i.e. Entrust, etc.)
Delegate is generally more lethal to target insects and doesn’t break down as fast. Delegate is not certified organic, like Entrust, but I don’t believe you are an organic grower anyway.
I came across an efficacy study of insecticide for thrips on the Web (in lettuce).
http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1177-1g.pdf
I didn’t read the whole study, but in the conclusion, they said Success was the best stand alone insecticide to control thrips. Success has the same active ingredient as Delegate.