I would be bold and say you won't lose 30lbs by July 4th. 9 weeks or so means a weight loss of 3lbs a week plus a bit more, and I just can't see that as being possible.
However, no one is going to weigh you on holiday
With a good diet and exercise regime I bet you can *look* like someone who has lost 30lbs!!!! For example, this year I have been exercising and eating healthily, and have lost 4lbs (having lost 60lbs last year) however, in the last 6 months I've dropped from a size 18 (US14) to a 16 (US12) and have had countless comments about how well I am doing this year
Which is cool, sometimes the scales don't really reflect what we are doing to help our bodies.
For me, going it alone is fine, I use support here, and at my gym, and I find systems like weight watchers not very good for me, because I get caught up in comparisons, competitiveness, and basically not feeling good enough. It doesn't happen to me with online support, because we are so honest here.......and there are so many of us with different experiences.
But the whole thing with weight loss is you gotta find what works for you, if that is weight watchers, go for it!!!!