my husband and I are moving to Seattle from the UK. Anyone have any tips on where to live, things to do, things to avoid, places to go, places to avoid?
Is it also true that if you are there on an L1 and L2 visas, you have to leave the country every 3 months, even if it's for a night? Just sounds strange to me!

I can't help you about Seattle...but no you do not need to leave the US.

Traffic is horrendous, the mountains are beautiful, avoid standard commute times/routes, go hiking.

Yup ^^^

That is incorrect, as Jerseygirl mentioned.

One thing that I wasn't immediately aware of when I received my L1 visa is the that visa does not allow any moonlighting, so your husband cannot do any side work for a different employer (or even himself). Just something to be aware of. It might be very tempting to do side projects for people (or a small startup, perhaps) but it isn't allowed.

Lucky you! I was just in Seattle on a bit of a reconnaissance mission as I am looking to move back to the states with my family (I am a USC) but it doesn't look likely at the moment as house prices there are INSANE. Be ready for traffic (lots and lots of traffic) and if you're buying a house, get yourself a very good realtor as competition is fierce. If you have a vague idea where you're looking to settle, PM me and I'd be happy to share what I know.

LOL you've clearly never lived in Los Angeles.