I believe the speed-limit indication is driven by the flap handle position; you can see that because it moves instantly when flaps are selected. However, the amber minimum manoeuvre speed indication, and the stick-shaker threshold indications move in accordance with actual flap position; again this is clearly visible when flaps are running. So, provided it is just an indicator problem, and not a FSEU failure, you should be able to rely on those indications to assist your decision-making process in an emergency. You can also look out of the cabin windows, of course.