I just flew through Lisbon Portugal yesterday on my way to Madrid from San Francisco. I flew with TAP airlines.
TAP airlines checked my test before allowing me on the plane. That was the last time I was ever asked to provide anything regarding test results. On arrival in Lisbon airport I was not asked as I went through border control and neither was I asked preflight to Spain or when I arrived in Spain.
I took an antigen test the morning before my flight because it was the cheapest option and Portugal accepts it now. Doesn’t have to be NAAT or PCR, although those are better tests. Check the Lisbon airport website, it has lots of detail about what tests are acceptable.
For testing places there are like millions in the US so I don’t think that would be helpful but I just googled testing sites in Pali Alto and was given 15 options of places to get it done around me. Results took less than 40 minutes to get back.