All the boats mentioned will perform OK in the 8-12 range (obviously the more wind the better). To get better performance you'll generally need something lighter and/or larger, both of which I see as potential liabilities working in surf. I want quick maneuverability and strength. The Hobies come alive at around 11- 12knts, and for me you just can't beat their simplicity and durability.
As for singlehanding, I've never single handed the 18. The ability to furl a jib is a big plus. Any of these boats will be awesome and potentially bordering on being a handful single handed in 18knts. How much do you weigh? Righting singlehanded is also an issue. There are water bags, shroud extenders, and Power Righters ( I have not used Ricks, which looks pretty cool), all of which have pros & cons. I love to single hand, but I rarely do it without some kind of backup, either on the water or onshore. Singlehanding on the ocean with an offshore breeze is not advisable. It sounds like you get an onshore sea breeze most afternoons which should be great.
The temp here was in the teens last week, but should be kissing 70 today and tomorrow. Think I'll go work on my boat.