I am coming from winging and tow foiling, very comfortable on foil at this point, and looking expand my skill set. No experience surfing but want to learn to prone foil.
Is there any utility in learning to surf first without a foil? Looking for any guidance on set ups, reading waves, conditions and techniques. Thanks.
Winging in waves will give you the wave reading knowledge. You don’t need to go to longboarding first. I would just wing in waves if I was you. 
Catching waves with a foil is bloody difficult even for very accomplished surfers. The positive being that you can skip the surfing and dive straight in, just be patient and start small. Also, put some work into finding a wave with a gulley so the wave breaks and then fades