Hamlin is often planted in solid blocks in the commercial groves (sometimes a mile or more from any other citrus) and I have never noticed any polination issues. Actually, Hamlins tend to bear heavier crops than Valencia (when not affected by HLB) which would indicate better pollination to me if anything. I don't know much about Ambersweet because it has not been planted much around here. If my memory is correct, though, it has some Tangelo parentage (Orlando). A lot of Tangelos need cross pollination to produce their best crop, so pollination might be a concern there. With your Hamlin also blooming, though, I don't think that it will be an issue for you.