Just curious if anyone has any experience in traveling from WDW to Universal Orlando. The plan is to spend the day touring Magic Kingdom and then transporting to Universal. I’m not planning to rent a car and am staying at the Polynesian. Obviously I will have checked out. Will they hold bags for me, etc. Any advice, tips, experience would be great. Thanks!
Since you are not renting a car, I think your only options are Lyft, Uber or a taxi.
Found this on Touring Plans website…
Getting to Universal Orlando from Walt Disney World
Driving from Walt Disney World to Universal Orlando along I-4 takes about 15 minutes with light traffic, or as much as 40 minutes during rush hour. If you’re staying at Walt Disney World and you don’t have a car, Mears Transportation will shuttle you from your hotel to Universal and back for $21. Pickup and return times are at your convenience. To schedule a shuttle, call 
855-463-2776.
From three Denver college-aged women who tried Mears:
We took a Mears shuttle from Disney to Universal, and we don’t recommend it. It takes a very long time to get you there—it stops at SeaWorld and a couple of other places before Universal—plus we waited 45 minutes for the shuttle back to the hotel.
Taxis and ride share services (Uber and Lyft) are also readily available to and from the resorts. A one-way taxi ride is between $35 and $45 (plus tip) depending on which Disney hotel you are leaving from, and may be cheaper than a shuttle if you have three to five people. All transportation services drop off at and pick up from the lower level of Universal’s main parking hub, from which you can walk to CityWalk and the parks.
There are also deals out there that combine transportation with the universal ticket.
See if this helps you figure out how to get there:
The Poly will hold your bags in bell services for as long as you need them to. After leaving MK, go back to the Poly and have your transportation pick you up there. I highly recommend Uber over a taxi because it is tremendously cheaper.