Hey John,
I should imagine that ballooning in busy controled airspace is probably not recommended as i should imagine you know balloons have priority over gilders and flying machienes. (would mean a lot of dodging around you) but i have never been in such a situation so not sure how valid my contribution is. You could try writing to an ATC department or a local busy airport to see their views and what they would reccomend.
Hope its some use
Wing Nut
