I visited WDW and saw everything I wanted to in MK (which has fewer rides than DL) in 1 day, and then a good taste of Epcot and some of Hollywood Studios together in my other day. So you can have a great time!
Are you just going to Disneyland Park and not DCA, then? If I had JUST one day I'm almost certain I'd choose DCA, but I've also been to Disneyland a bunch of times. You could get a park hopper but there is SO much to do, you could definitely spend a whole day in DL and not see it all, and likely do the same in DCA (though there are more "film" rides over there that you can see in WDW).
In addition to Pirates of the Caribbean, do not miss Space Mountain! (unless you don't like turbulent roller coaster rides in the dark
) Finding Nemo Subs are unique to Disneyland; it's not my favorite, but my friend who's from Florida wants to see them. The Sailing Ship Columbia is unique as well, but it usually only runs when the park is busy, or when the Mark Twain is down. The monorail return trip into Disneyland is really neat, but if park hours are short or lines are long, I wouldn't bother.
If they are offered, our springtime fireworks and Fantasmic! are both excellent and worth seeing, though I think I'd just pick one. If they're running and I just had one day and was from WDW, I'd pick Fantasmic!--I think the fireworks show is more meaningful for Disneyland fans, and it is more likely to be canceled due to wind (which would mean you will have wasted all that time waiting).
"Can't miss" food is subjective, of course. Many would say a Monte Cristo (served at Blue Bayou for lunch or Cafe Orleans for lunch or dinner) can't be missed. The atmosphere in New Orleans Square is great so I'd definitely either eat there or at least get a snack there, if anything appeals to you. I enjoy mint juleps, but they're pricey and a lot of people hate them. (If the hours are short, I hate to spend the time at a sit-down restaurant, but it looks like you'll hopefully have Spring Break hours.)
There's a fried green tomato sandwich just down the road at Hungry Bear Restaurant (counter service) that's unique and good if you like that sort of thing. Redd Rocket's MAY be getting a new menu since it's under refurbishment right now....I haven't heard rumors of a new menu but most restaurants that have been refurbished in Disneyland have come back with changes, so we'll see.
You can see current menus at
http://www.wdwinfo.com/disneyland/dining-Disneyland-Park.htm
Have a great trip!
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Thank you for posting such detailed information, especially comparing WDW to DL 
