I had the same problem with my EliteBook 8530p. I didn't manage to get both speakers and headphone jack to work at the same time, but that was over 6 months ago so I really don't remember how the things were.

Here is a link to my thread: http://forums.unixhub.net/showthread.php?tid=424

Idea if you get to the same state where I was; So you have speakers and headphone jack working but not at the same time (e.g. you play sound from speakers and plugin your headphones but the sound only comes from speakers), try to find a way to detect when you plugin your audio jack and change the audio output.

And as NeoTerra already said, you should try the FreeBSD forums, there is really experienced guys there.