sounds like fun! vegas is such a great place!
i'm not sure if you're looking for an easy way to drop the weight- sorry to say but if you want to do it, you have to work hard!
11 weeks is a decent amount of time so you should be able to do it. this is going to be no surprise, but you have to be sure you're burning more calories than taking in. weight watchers is a good idea to learn portion control; however, i know a lot of people who went on ww and they easily gained the weight back when they stopped.
if you incorporate exercise you will help your body become a fat burning machine- you will burn calories just laying around because of the muscle you build. also, you'll be able to keep the weight off.
i don't know your activity level now so it's a shot in the dark with how much you can do now. a good mix of cardio and weight training should do the trick. work out 4-5 times/week. rest in between days you do weight training and then the other two days can be cardio. for weight training, you always don't have to use weights; you can do body weight exercises like sit-ups, push-ups, squats, etc. just work all parts of your body equally- not just the area you want to lose fat. for example, work your quads by doing standing squat with just your body weight. you can also do lunges, too. do sets of 12-15 reps and do 3-4 sets of these. you should also do something for the back of your legs (hamstrings)- google hamstring exercise and you'll see some of those work outs too.
for upper body, push-ups are wonderful. if you can do regular ones, do the ones with your knees on the ground. that is a great work out for shoulders, chest, arms, and back. also, do sit-ups (both crunches and full ones).
for cardio, do whatever can get your heart rate to your target heart rate (220-your age x .75). do some brisk walking or running or jumping jacks or jump rope or bike riding. you can go out dancing too, but just remember, your goal is to get your heart rate up. start making your life more active by taking the stairs instead of an elevator, park farther away, walk to the grocery store, etc.
be sure to do cardio for at least 25 minutes 2-3 times/week. a fat burning secret not many know about is interval training- run (or some other cardio exercise) for as fast as you can for a few minutes. then either decrease the same activity for a couple minutes and then repeat. or you can do some of those body weight exercises in between your cardio sessions.
good luck! whatever you do, stick with it and try not to get discouraged.
also, if you need a partner to help motivate you, don't forget to ask your husband.