I was going to suggest
Abhayagiri Buddhist Monastery in California.
It is in the Thai Forest tradition of Ajahn Chah. Ajahn Amaro and Ajahn Sumedo are both associated with this monastery and both are on the opposite side of Ajahn Brahm's teaching methodology. and therefore closer to Tan Geoff's brand of teaching.
Unfortunately, they are not set up to take retreatants. Although this looks promising (click on "Overnight stays") and you may want to check into it:
First-time visits are limited to a one week stay (or ten days if visiting from out-of-state or two weeks if visiting from outside the U.S.). We ask that all new guests stay for at least three nights. After the first visit, a guest may request to stay for a longer period of time when returning for a second visit. Accommodations are limited, so please contact the guest monk (preferably by email) well ahead of time, to check the availability of space. We do not make reservations for guests more than two months in advance of the requested date of stay.