Still go to Uni, and get express passes. Its spring break here in FL. expect 60+ minutes waited
When you have mono, your spleen swells up meaning that rough activities can cause it to rupture...thats why the question about Magic Kingdom vs Universal was presented (Im assuming, correct me if Im wrong OP :thumbs
...so just saying go to Universal and prepare for long waits on FJ is completely unhelpful because that is a ride the OP will probably choose to avoid.
That being said...
I had (have) mono, and was diagnosed on the weekend of my Grad Nite at Disneyland...it was a huge bummer but I was so determined to go that I powered through it. I went on the thrill rides (Indy wasnt around yet, but the roller coasters were) and had no problems. Granted, I probably should not have done these things but I was ok. It really all depends on YOU, how YOURE feeling, and what your doctor says, because everyones experience with mono is different. Magic Kingdom has a ton of rides that wont put any pressure on you; the highlights (Fantasyland, POTC, HM, etc) are slow and dont have restraints that jab into your affected area. However, things like FJ, Hulk, Dragons, etc are not only forceful but have restraints that will push down on your spleen and potentially cause pain. Rougher rides will also cause some discomfort (I got off the Matterhorn with a noticeable ache, but kept going because I was stupid
). I would never advise someone to risk it because mono can be very dangerous HOWEVER depending on how youre feeling and how youve dealt with it, thrill rides may not be an issue for you.
Another thing to consider is that you will be tired for your trip. Mono wears you out bad, and Magic Kingdom is a much slower-pace park. To conquer all of Universal and IOA, while very possible, is kinda hard to get done without taking rest breaks that you will undoubtedly want to have. Keep this in mind.
The good news is, no matter what you choose to do, both are incredible theme parks, thrill rides or not But its your body, you have to decide whats best. Just be safe, and have a great time!