If you're staying at hotels, you don't have to worry about this because they'll register you. If you're staying with friends, registration is easy enough (they should no which PSB is responsible for them), but I usually don't stress this issue (call me crazy... no problems yet apart from a mild scolding once during the course of 12 years).

I must say that I'm a bit surprised by your wife's friends' paranoia because that certainly doesn't reflect the sentiments of any people I know. Perhaps they lived in a diplomatic compound, and didn't get out much?