Yes. Depending on whether you're referring to hidden or found, the methods differ. And if you're referring to caches found there is a limit of how many can be mapped at once (technically there is for hidden too, but that's less likely to be an issue)
For caches hidden by a user: On the landing page of PGC, go to Advanced search and enter the username in the Cache owner field. After it's given you the results, click on the icon just to the right of the VGPS ones at the bottom of the table, with hover text "Plot selected/all on map".
For caches found by a user: Use Map compare (in the Tools menu). Enter the user name under Profile name. You can leave Compare with empty. Select "one found" and add the filter "Show disabled/archived" to get the caches which are no longer active. You might need to add an area filter if the user has found too many caches (I think the limit is 10,000).
