Not an expert on any scenes or sure what you mean exactly, but I have been to a few meetup events for the San Diego JavaScript Meetup.com group, and they are definitely mentioning this "startup scene" thing as though they are part of it. There is some overlap with the SD Ruby meetup.com group people. They have a meeting on Tuesday http://www.meetup.com/sandiegojs/events/41414182/ Meets at 3rd Space http://3rdspace.co/.
Besides 3rd Space there are also places like Co-Merge http://co-merge.com/ and the Hive http://www.hivehaus.net/ where some startupy types are sometimes. There is also an HTML5 meetup.com group.
Besides 3rd Space there are also places like Co-Merge http://co-merge.com/ and the Hive http://www.hivehaus.net/ where some startupy types are sometimes. There is also an HTML5 meetup.com group.