San Marino, Italy

Are you referring to the Republic of San Marino, which is an independent country, not part of Italy?
Or are you referring to the town of San Marino in Italy, which is near Mercato Saraceno?
If you are referring to the former, it is worth it if you have already seen the major locations of Italy or if you happen to be near the area.
If you are referring to the latter, I wouldn't bother.

If it is San Marino, Italy you mean, there is literally nothing to see or do there. There is barely anywhere to stay. I'd spend my 2 weeks in Florence, Venice, and Rome,

I stopped in San Marino for an afternoon and enjoyed walking around the little town. The main reason I went was to be able to cross off another "country I've been to" on my list.
It is small and at the time there were some tour buses that stopped there, for the same reason.
Nice view from the Ramparts.
I say - go while you have the chance.

I am indeed talking about the independent country of San Marino located within the country of Italy.

I've wanted to see San Marino since I did a report on the place in 4th grade and we spent one night there last May. This year we're going to spend three nights there and plan on visiting the Ferrari Museum in Maranello, a neighborhood in the tiny republic. We liked the place and being there in early May we missed the hordes of tourists.

I've traveled in Italy since 1980 and since 2005 we spend a month there every year. It's my happy place, so spending more than an afternoon in San Marino is ok with me.

Buon viaggio,

San Marino is not on Rick's must-see list, but he did re-visit it for TV purposes: http://www.ricksteves.com/watch-read-listen/video/tv-show/little-europe.

Laura - I saw that on TV last fall which is what made me want to go there however, he doesn't have anything else anywhere about it. Should I take it that he doesn't feel it is worth going to see?

Rick had lots of good things to say about San Marino in the TV show so I'm sure he thinks it's worthwhile. However, if you have just two weeks to spend in Italy (and have never been before) there are many other things that most would tell you are "must sees" beforehand.

San Marino is a great place to visit. But it probably shouldn't be at the top of your wish list unless you're hoping to (like someone else said above) "check off another country" on your bucket list. It is a little bit out of the way on the main train lines and would take up precious sightseeing time traveling to and from. Weigh your options carefully. Check train times. See how it corresponds with the other locations you want to see, and that will tell you if it is ultimately a good fit for your itinerary.

In the end, you should take everyone's advice (even old pros like Rick) with a grain of salt. No one can tell you for sure what you will enjoy. They can only tell you what they experienced and about the things to see in each location. In the end, you'll need to decide the things/places that sound most interesting to you and jump in for the adventure.