I strongly believe that a tiny population of dinosaurs survived in the jungles of Africa long after the extinction but they eventually died out due to the lack of genetic diversity, human hunting, or etc. Or maybe a smaller, dwarf version of said species, which is why they were so hard to find.
Anyway, there probably were dinosaurs who survived the extinction for quite some time, but they're definitely all extinct today.
Given that there are still uncontacted tribes in the Amazon rainforest, this is a possibility.
I don't think it would be possible for dinosaurs to live up in mountains though.
It's too cold for them.