Just as an FYI, I was able to walk into the Best Buy store in Costa Mesa, CA and purchase an S2 42mm Space Grey last night (around 8PM), albeit not without some back and forth with the sales person.
I used the strategy that others have recommended of clicking on the "Pick Up Today" tab and changing the store until one in my area showed the model I was looking to purchase. As has been mentioned there is no way to reserve the watch online, and in the case of the S2 42mm SG (at least of of last night) there wasn't even the option to pre-order.
The two stores in my area that showed the S2 42mm SG were the Costa Mesa store, and the Downey store. Since I'm in Orange County I opted for Costa Mesa.
When I arrived I spoke to the two sales people hanging out in the Apple area. Both were adamant that they didn't have any S2 Apple Watches in stock. One even said he'd turned 3 people away earlier in the day and had just checked "the back" a couple hours prior. I persisted and after a couple minutes one of the sales people mentioned that they had just received a truck and he'd check one last time.
After a few more minutes he came back out to the sales floor and said something along the lines of, two hours ago we didn't have any, now we have a bunch. From that point it took all of about 3 minutes to finalize the transaction and leave.
For the record I have no idea what "a bunch" means, nor which configurations they had/have but I thought I'd relay the information here if anyone was in the Orange County, CA area and looking to pick one up.
Lastly, I was a very earlier adopter of the original Apple Watch. Having been a 'watch guy' most of my life I was excited about the possibilities of finally making the leap to a 'smart watch'. I purchased the stainless steel and poured close to another $500 into bands. Unfortunately the experience left me feeling as though the Apple Watch, specifically WatchOS was an incomplete product. It simply felt rushed. After only a couple months of use I sold it, and assumed it would be a very long time before I was willing to give it another go.
I'm happy to say the Series 2 is a completely different animal. The OS feels so much more refined and the speed is night and day. If you're on the fence, don't hesitate.