Let me add my two cents worth. I was in almost the exact same position as you 12 years ago. My girlfriend's father had taught me to sail 20 years earlier (just before she dumped me
), and I had a lake that I wanted to sail on with my wife.
I did exactly what you suggested - I went looking for a Sunfish. I ended up finding a Phantom, which is almost identical to the Sunfish but with a slightly larger, more comfortable cockpit that both of us could fit into. After 10 years of sailing that, we upgraded to our current Catalina 250, but we still have the Phantom and sail it 2 weeks a year on the lake while on vacation. We still love that boat.
You'll learn a lot from joining a club, or finding someone to take you out. But don't be afraid to just go out and buy a boat if you want to get started on your own. If you can find something used with a trailer for under $1000, the upside far outweighs the downside (assuming you have a place to store the boat for free - like a back yard).
I do agree that something like a Capri 14, Flying Scot, or a Thistle has a lot more space for two to stretch out. Some of these are sloop rigs, which improves performance, but can be a little more complicated to rig at the boat ramp.
Ease of trailering and rigging should be a consideration. Be careful about advice that begins with "for only a few dollars more you can get..." because it's about more than just money. It's hard to beat the simplicity of the lateen rig of a Sunfish, Phantom, Scorpion, Aqua Fin, or any of the other dozens of Sunfish clones. But space for two is very tight on them. As with everything involved with sailing, there are compromises and tradeoffs.