You can check rates with all of the major car rental companies for pick-up at one of the hotels located along Hotel Plaza Blvd. across the street from Disney Springs. These can be a reasonable walk from Saratoga Springs, depending on where you are located within the resort. I’ve picked up Alamo or National at the Buena Vista Palace. There’s a sticky at the top of this thread listing the various car rental locations at WDW.
Sometimes, the rates for WDW pick-up and MCO drop-off are much higher than rates for MCO pick-up and drop-off. In that case, I have used Magical Express to get back to the airport and then driven back to my resort to pick up DW and our luggage prior to driving to VB. Last time I did this the MCO-MCO rate for a weekly rental was less than one-third the WDW pick-up with MCO drop-off, less than $200 compared to more than $600. Other times, picking up on-site was only a minor or zero premium compared to going to the airport. Rates vary greatly depending on demand for cars on site at WDW, so YMMV.