So, I want to lose 15-20 pounds in about 6 weeks. Is this a good lifestyle plan to achieve that? Any advice?

You seem to have the balanced diet part down, all you need is to engage in an activity you like/enjoy. You will burn a lot of calories playing racquetball (specially if the courts aren't cooled down in summer). Martial arts (especially Taek Won do) is also a lot of fun and its a good workout when you push yourself. Neither of the two require you to be athletic when you start, but you can enjoy them and develop your abilities + physique. Just a thought..