There is a back way in, but depending upon where you are coming from, it isn't a short cut. It is most convenient for driving coming from DTD, and OKW, etc side of WDW. We used it frequently coming from OKW to the WL, Poly and to CR.
Take the road that runs by POFQ and POR and go past those resort which will be on the right side of the road (I think this is Bonnet Creek Parkway; when that road ends, you'll turn left onto Vista Parkway and pass the golf courses, etc. This road runs into World Drive leading to CR and WL just past the parking entrance to MK, turn right on World Drive, then right onto the road leading to WL.
There used to be a security gate on Vista, but it has been closed for several years now.