Yes, you can still use old park hopper pluses at Pleasure Island.
Unfortunately though, Disney changed the ticketing system around a little bit, and the way Pleasure Island is currently setup, older Park Hopper Plus passes do require some special attention.
You either need to stop at the ticket booths out front of Pleasure Island and have the tickets updated ( not upgraded, not re-issued, just updated for the new system. ). They re-print your PHP+ tickets onto a new paper ticket with the same useage that you had before. This whole process can take about a minute or so ( depending on the CM ) per ticket.
The other option, and the preferred option, is that two clubs still run on the old ticketing system. You can take your tickets to COMEDY WAREHOUSE or ADVENTURES CLUB first, have them scanned, get your stamps and wristbands, then go where ever you want. This is often faster.