Hi Gaperbob,
Three months ís pushing it imho. Just riding and be able to say you've 'done' it, or be able too say you've actually see something of the beautiful countries you passed!

But it all comes down to personal preferences and posibilities.
As for relevant advise...
For sailing from Panama to Cartagena you can contact
Backpacker Hostel Wunderbar - Home a few weeks before you arrive in Panama to know which boat you can take with your bike. (from personal experience : try to stay away from the MetaComet!!) There are a few boats shipping tourists with enough room for bikes, but schedules are not fixed, so you might end up waiting.
Looking at your timetable, you might reconsider and skip the San Blas islands and fly from Panama City to Colombia, little more expensive, saves at least about 4 days. And spend those days in Colombia, you'll need them

From my experience bike paperwork can take a day in the port customs and, from what i heard, is way easier when flying.
If you do decide to sail, make sure the captain covers your bike properly, salt water can do damage to your bike which can cost you days further down the road.
Hope this info is helpful.
Suerte!
Sander