THIS CACHE IS NOT AT THE POSTED COORDS
This is a changeup from the rest of the Bike Trail series. 
It is a field puzzle. In order to get the final coordinates, you need to go to the location, get some information and do some simple math.
The final location is at n38 34.AAA w121 17.BBB
1. Count the number of picnic tables in the small park and multiply that number by 21. Then add that number to the last three digits of the posted North coords. That answer is AAA.
2. Find the 5 digit number at the posted coords, divide that number by the last two digits of the same number. Then, round that quotient up to the nearest whole number. That answer is BBB.
See?? Simple. Now go get the cache, it's a short walk down the Trail.
Congratulations to GCRiddler for FTS and FTF!!!
Wow, I intended this to be an EASY puzzle!! OK, for all you armchair quarterbacks out there, this is a FIELD puzzle. It cannot be solved with the internet. Get off your computer and get out in the field! Once there, find the CORRECT five digit number and the answer should be easy. I have added a hint for the first stage. Good luck!
You can validate your puzzle solution with certitude.