First of all, I hope that when you say that "both running HSRP for redundancy" you mean that there are a total of four routers. Otherwise I suspect that you will always have the phantom router idle.
You might be able to implement some type of policy routing to help if the above isn't an issue (to include policy by protocol and/or source address). But without knowing how your network is laid out, it would be pointless to make specific suggestions. Just remember that your policy applies to incoming packets. So if you wanted to test (match) traffic, you need to do it as it comes into a router. Then you can specify (set) which interface it leaves out on.
Also, with rare exceptions, I don't think you can influence the route that traffic from outside to inside takes. External networks will make those decisions on thier own. On that note, are both of your ISPs advertising both/all of your address spaces? If not, your inbound traffic will always be via the only ISP that is doing the advertising.
