Charlie has previously suggested to use stairs if hills are too much of a problem for one’s achilles. I’m coming back from an achilles tendinopathy myself at the moment, and have not had any problems doing hill sprints in running shoes on grass, however. I can’t imagine that plyos would put less stress on your achilles than hills, so I doubt that they would be a good alternative.
I would start with just a few easy hill sprints (i.e. 3x10, 3x20m at 85-90%) the first time round and then see how the tendon feels the next day. Also, i would not do more than two high intensity sessions per week for a while. I actually followed a program where I only ran every second day (i.e. 7 times per fortnight) always alternating between hills and tempo. Now I’m doing two hill sessions and two tempo sessions per week and will start running on flat ground (grass) next week. I don’t think I’ll be setting foot on a track for at least another month though.