Where to start? A preface that I took my nearly 12 y/o to see this who for the most part enjoyed it.
The opening 15 minutes are nearly unwatchable. I won't spoil it as it truly is something to behold. Dwayne Johnson knows it's awful and delivers the terrible exposition and leaps of logic required to get the story going with a pained expression. There is nothing to work with.
The story/script was reworked by Brian & Mark Gunn, the far lesser of the Gunn clan IMO. The film is loosely directed by Brad Peyton who came from shorts and after 5 years in the wilderness was given the abysmal Cats & Dogs 2 and now this.
The special effects fit in context and are some really nice work (a few bad water composites, but they are always difficult) and the 3D was solid enough and served a number of scenes well. Set design for the most part was good, though they often felt small relying on CGI to extend locations
So with the behind the camera out of the way, what do we have...
Once we get over the awful, preposterous, clunky, exposition laden beginning we [very] suddenly leave the US and are off on "an adventure". This is where we meet Luis Guzman and Vanessa Hudgens. Guzman is great in just about everything and I enjoyed him here; he knows who he is and why directors want him in a role. Hudgen's wears a tight tank top and short shorts for the whole film, leaving my son with many feelings to work through later. Michael Caine has fun, but again has little to work with.
There are a few quite funny moments; the pec/berry scene that is touched upon in the trailer runs longer and gets Guzman in on the fun and we found it really amusing, funnier in 3D. Both Johnson and Guzman have some good funny quips along the way that make you wish it were a better film.
J2 could have been a really good film if it had a better script, reworked exposition and maybe another 10 minutes for the audience to find the characters and care about them. It is just so by the numbers, you can feel yourself moving through it, and it didn't have to be.