Is there anyone at all you know that you would feel comfortable going with? Even if it is not a best friend, if it is just someone to bring with you it can be a helpful support. It helps if that person is a little more outgoing with you, because they take a little attention of you and you will feel less pressure to have to talk or be the center of attention. I don't know if this makes any sense, but I find it's very affective. IThere is someone I would normally never spend time with ('cause I don't spend time with anyone, usually), but when there is a social event, we go together and she loves to be the life of the party, so the focus is off me - then I feel more comfortable participating in conversation or whatever. Such a person can also help or lessen the pressure of other "challenges" you may find going out - like navigating your way through a crowd or driving in traffic or whatever your little adventure might entail.
You always have the option of not going - and avoidants use it often - but if you think there is going to be a chance you might enjoy yourself, every once in a while it is worth taking a risk. We, more than anybody, need the reinforcement of a positive social experiences. Sometimes I tell myself in advance that it's going to be terrible, so I have no expectations - then it turns out to be not half bad.
I am a BIG music lover... and as musch as I hate going out in public, especially in any kind of a crowd... I CANNOT live without live music. Acquaintances with me help to mitigate the anxiety of going to a concert - I feel safer with them, because I know they're good at doing what I'm not! Plus I try to lose myself in something else (like the experience of music) so I can tune out the crowd around me as much as possible!