First, be sure you understand the income tax impacts of anything you do.
As a married couple, you will receive $500,000 tax-free gain from the sale of your residence.
Your gain may or may not exceed that amount.
So just be sure you understand what tax if any is due on the sale.
My sense is that you are correct - when the market turns, your property in Sunnyvale will go up more in value than the properties in Amador County. So that might argue for you to wait a while. My sense is maybe 2 years till market turns but that is no more than an educated guess.
I would also imagine the market in Amador County must be VERY SLOW so my sense is that you will be able to make a very good purchase up there NOW. Someone with a lot of cash could probably strike a very good deal.
On another point, I understand the lure of no having no mortgage but consdering your age (you both will probably live another 30 years), it might actually make sense to get a mortgage at today's low rates and keep some of your cash. With inflation on the horizon and many more years life expectancy; you may not want to "pull in the reins" - you may want to keep investing moving forward.
I would get some financial planning advice to help you with this decision.
Bottom line, you are well-positioned financially but it is important you make the right decisions now because they will determine the quality of your life moving forward.
Another option is to buy now and move and perhaps rent Sunnyvale for a few years.
In the final analysis after getting proper financial analysis, I would just follow your emotions and make the move when emotionally the time feels right.