I highly recommend Martinas place. Its exceptionally clean and very modern. Quite close to the Castle and the Old Town (4-6 tram stops). Tram stop is a very short walk from the apartment. The neighbourhood is very quiet.
Prague is a beautiful City, the locals can be quite abrupt but I dont think they mean any offence.
Some locals speak a reasonable amout of English. You should always have 10ck coins for the public toilets.
Martina was a fabulous host. She waited at the apartment for us to arrive, we were a bit late. She was also available to message her if you needed anything. She also arranged our taxi back to the airport, which we were very grateful for.