Whatever your exercise regime, its important to work with your physician and trainer which sounds like the case. In addition to specific exercises to build lower body strength, a really important area not to neglect is overall "core" conditioning. This is the group of muscles that include the abs, obliques, lower back etc. In terms of balance and overall stability, this group of muscles play in equally important role, maybe even more so than the lower body.
Talk to your trainer about working some core training exercises into the routine. In general exercising the core involves challenging your balance - so the exercises you described in the original (leg raise & balance) post falls into that category. They will really help. Another great one is doing crunches on a swiss ball.
When sight fishing, look over your shoulder from time to time, you never know who's behind you