I had previously convinced the Simi Valley rec center (or officially, the Rancho Simi community pool) to allow tail swimming in their pool. I had swum there a few times over the winter.
Now, they are on their summer schedule. Also, if we want to use the pool for a get-together, summer is preferred in any event. But, they operate the pool differently in the summer. Today, I checked it out.
Lap swimming is open from 11 AM to 1 PM. During this time tails are allowed. They do not actually use lane dividers, and swimmers are asked to swim across the pool in the short direction, 25 yards. During my visit, no one was swimming in the deep end, where there is the 15 foot deep diving well. They had no issue with me swimming down to the bottom of the well with my tail.
After 1 PM, the pool switches over to recreational swimming. If you stay, you are supposed to pay the $3 fee a second time. They put up dividers to set aside a few lanes for lap swimming, the shallow end for children, the aqua obstacle course, and the diving area. No pool toys, including fins and tails, are allowed.

If we want to meet there, 11 AM to 1 PM is when to do it.