If the last hop *and* the hop before it are both showing similar packet loss, then it's almost certain that the problem is with the ISP, not his router. In most cases, the publicly available IP address (that you're pinging) is his router, and the one before that is part of the ISP. If that's showing problems, then the ISP is probably the culprit.
This is based on "usual circumstances", not this specific instance. It's hard to get an exact story of the problem when tracing from the far side - there are numerous things that could mean the above conclusion is wrong.
- Pete