I never use my title outside of my professional circles. Professionally I never use it myself, but I accept if others do it to introduce me to someone. I don't accept it because I think I'll be more respected, but because I know it cuts short the conversation and avoids embarrassing situations. Although I enjoy when someone mistakes me by an undergrad student (I look young yay!), others may be offended and the person asking gets embarrassed on both situations. Also, if someone is looking for a student or a senior scientist for his/her group, doesn't have to waste time talking to the wrong person. To avoid introducing myself as Dr., I usually just say my name and that I work as a postdoc at X, and that gets the same message across. Don't get me wrong, I'm not against people using their titles. It's totally up to each individual to use it or not. I just don't like to use mine. To explain you why would probably take another very long post, so I won't go there.
Today I came across a very funny text about the use of titles in Portugal. I laughed a lot with it because it reminds me of funny situations I have been through. The "Drs." the author talks about are not PhD holders but people who have an university degree. It is also not uncommon to find people without any university studies call themselves Dr. and demanding that others do so, just because they have a certain status (common among politicians or people working in the city hall and similar, but not only).
The only time I used my title outside of work was with one of these "Drs.". I needed some sort of paper and the clerk told me she would have to see with the "Dr." if I could have that or not. Although it was 10 am, the "Dr." was not at work yet, which is also not that uncommon. My mum was with me and while we waited for him, she told me that she used to know the person who worked in that position before, but he had troubles finishing high school and he was no Dr. at all, so it must be a different person now. Some time later the clerk points out a man coming in and tells us to talk to him ourselves. My mum tells me, in a whisper, that indeed it is the person she was talking about before. When we approached him and he introduces himself as Dr. Y (in a very cocky way I must add), I couldn't help it but introduce myself as Dr. Sara C. I had just finished my PhD. I was 26 and I was dressed like I was 20. He looked very confused. He never asked me anything, but I could see he wanted to. I got my paper and when we walked out we couldn't stop laughing.
I'll leave a bit of the text I found below, and if you want the full version is here (first in Portuguese and then in English).
Lucy Pepper in Observador