I too, was very interested in Plan 6 of Canopy Park, as it has 4 bedrooms and as large as regular single family detached house. Ultimately I decided that I wanted a backyard (however small it may be) and my wife was a little skeptical of a 3-story home (just lazy). Here’s my take on your questions:
1) Yes, the builder is very willing to negotiate so don’t feel embarrassed to bargain hard. They are already willing to give you $15K in flex cash but you can always bargain for more. However you should get pre-approval by their lender so that they know you’re able and serious. Right now there’s a Plan 6 asking for $399K:
2) 52 is the busiest of 3 nearby freeways. Most people take 125 to go to East County and South County so the traffic should not be as congested.
3) evolusd pointed out an issue I haven’t factored in before, which is the “hum” noise from the light towers. My lot is directly adjacent to the park (my backyard faces the street) so I don’t know if that’s going to be an issue. Hopefully in the interest of saving utility cost, night games will be limited. In any case, if you buy a home inside the community (not facing the street), I don’t think you’ll have much to worry about.