The web is replete with information about lavender (more), so I'll only add that the cultivar 'Provence' is purported to be moisture-tolerant, making it better suited for maritime climates. I've not noticed it performing any better or worse than other lavenders in the garden, though.

There are a number of lavender festivals around the world, including some in Washington state this upcoming weekend (for example, Sequim, WA). I'm fairly certain, though, that France is the best place in the world to see lavender fields.