By LAURIE KELLMAN SINTRA, Portugal — The doorbell to Martinho de Almada Pimentel’s house is hard to find, and he likes it that way. It’s a long rope that, when pulled, rings a literal bell on the roof that lets him know someone is outside the mountainside mansion that his great-grandfather built in 1914 as a monument to privacy. There’s precious little of that for Pimentel during this summer of “overtourism.” Travelers idling in standstill traffic outside the sunwashed walls of Casa do Cipreste in Cintra sometimes spot the bell and pull the string “because it’s funny,” he says.