Not IMO. Ankle weights are an old false attempt at conditioning the core strength of your body. To haul any weight in a pack vs on your ankles works very different muscle groups. Ankle weights only add stress to inherently weak parts of the body. Ankles were designed to provide lateral and horizontal stability to the human form. Core muscles of the torso, shoulders, and glutes provide structural stability with heavy loads.
Think of those times when you've walked across a muddy field or sloppy terrain and ended up with heavy boots...at the end of the stretch, the hip flexers are smokin, but if you carried the same weight on your back, hip flexers aren't smokin.
Losing 10-lbs of body mass before summer conditioning will improve your stamina and strengthen your knees (patella, ACL, PCL, MCL, and LCL) in the long run. A stronger body is by far the best approach. With this approach, each day your afield you'll lose pack weight (1-2 lbs per day), which improves your performance.
Ankle weights are not ergonomically sensible. If you want to become a stronger backpacker, train your body posture and muscles with a backpack...
larry