Ok I will answer at the risk of sounding like a flamer (I have too much respect for the people on this forum to pull that crap intentially).
For future reference
Ask the following questions:
1) how important is technique development in Wing Chun?
If the heart of the answer places technique develoment as a high priority then forget it. Wing Chun is about energy, structure and then concept, technique flows from the preceeding three. If someone is focussing on the technique, then they have a failure to look beyond the finger or in laymens terms, they cannot see the woods for the trees.
2) how important is the sui lum tao?
If they give the Sui Lum tao an equal or lower importance than the other forms then forget it. The Sui Lum Tao is the most important form, from the Sui Lum tao you gain all of the energy develepment and structural frame work for the entire system. All of the the other forms are extensions of ideas already found within the Sui Lum Tao, it is the most important form, as it lays the foundation of the system. The stronger the foundation the stronger the fighter.
3) What order do you teach the forms?
Once upon a time I thought that this was relativly unimportant, the further I progress in Wing Chun the more I understand that the order the forms are taught are extremly important. First the SLT for fundamental energy development (leverage) then the chum kui to learn how to utilise this energy with subtle changes to "find the bridge", then the Bui Gee, to learn how to devlop this energy right up to your had (wrist and shoulder joints, sometimes called whirlpool energy) then the mook, the reason why the mook is trained after the first three forms? Simply because if you have not developed the appropriate energy and structure, you will find that to approach the wooden man, is to do so utilising the wrong kind of energy. Finally the weapons are taught simply because they utilise the energies already developed and learn to focus that energy into a single point, which is moot if you have not already developed the proper energy.
These are the fundamental questions you whould ask and the red flags to look for, others will disagree, this is the wisdom I have gleaned from my Sifu