MCO is my home airport, and I have dealt with this for some time, so I want to make this very clear for those traveling here.

MCO's main building has 4 floors, in descending order: Level 3 (Departures), Level 2 (Baggage Claim / Arrivals), Level 1 (Ground Transportation), and Tunnel/Parking. When you de-plane at MCO, everyone must first take a tram from their gate to get to the main building. Once you exit the tram, you are on Level 3 (Departures) of the main building.

If you checked bags, you should first determine which "side" you need to go, A or B, before exiting security. If you flew with an airline in Terminal B (American, United, Delta, etc.), then follow the sign towards side B and go down one floor to Level 2. If you flew with an airline in Terminal A (Southwest, JetBlue, Alaska/Virgin, etc.), go down a floor to Level 2 on side A to pick up your bags.

If you didn't check bags, just stay on Level 3 and walk outside onto the curb. If you picked up bags on Level 2, go outside on the curb of Level 2. Every curbside area outside every door in MCO has a door number someone standing outside or driving by can plainly see. Door numbers for Levels 2/3 and Sides A/B are all unique. Remember which side/Terminal you are on, whether you are on Level 2 (Baggage Claim / Arrivals) or Level 3 (Departures), and the DOOR NUMBER you are standing under.

Now, when you want to call an UberX, you need to drop your pin (toggle the map inside Uber's app to position the pin at the center of the screen) anywhere OUTSIDE the airport. Smart Uber drivers do camp near the airport even though they know the airport is restricted. My recommendation is to drop your pin it just north of the center airport border near Highway 528 and Semoran Blvd. Once you see your Uber driver, CONTACT THEM IMMEDIATELY to tell them where you are. Sometimes, their English isn't perfect, so be clear in telling them:
1) You called an UberX, but you dropped a pin in the wrong place and need to be picked up at the airport.
2) Which Terminal you are at, A or B.
3) Whether you are at Arrivals / Baggage Claim (Level 2) or Departures (Level 3).
4) Which Door # you are standing under.

Most drivers will "get the picture" immediately. Just tell them something like: "Hi, I called for an Uber. I dropped a pin just outside the airport, but I'm at the airport now. I'm in Terminal B at the Arrivals / Baggage Claim area. Please come pick me up at Door 23."

It's very tough for them to screw up if you keep repeating: "Terminal B, Arrivals, Door 23". If their English is no bueno, you can use Google translate.

UberBlack is located on Level 1 (Ground Transportation), which is essentially the same cost as a Mears/yellow cab, or 3x the price of an UberX. For instance, my house is 20 minutes from the airport, and it costs $20-25 on an UberX. An UberBlack costs $60-70, and you get a nicer car. By nice I mean the last time I got an UberBlack at the airport it cost me $65 for a Chrysler 300. ROFLMAO. It still beats the crap product Mears is putting out there. Think New York taxi.

Mears is the classic local monopolistic taxi company that charges 3x what it costs an UberX with bad service and old cars. If you take them, you have joined the millions of tourists who get fleeced each year. To be clear, no person from Orlando in their right mind would ever take Mears or any yellow cab company. I literally have a physical urge to to pull tourists out of Mears cabs when I see them get picked up. Corruption is not rampant in Orlando as other parts of the world, but it is alive and well when it comes to Mears/yellow cabs at MCO.