How many suitcases in a Lyft XL?

Depends on the number of passengers

LyftXL are SUVs or minivans, such as Toyota Highlander, Kia Sorrento, and Dodge Caravan and are designed for up to 6 passengers (not includingi the driver). 

For luggage and suitcases, you will have access to the trunk space, but you can also utilize the space not occupied by passengers (within reason).  This means that if there are only two or three, of you, you will have space in the empty seats.

Here's a great guide:

ippei 1202

Uber Driver, CEO of TaxiFareFinder and Unleashed, LLC