Pup loves meeting other dogs and does so politely at shows, classes, close range etc, but put us in a park with a dog of any breed/size/etc up ahead and he barks, lunges, jumps, twirls etc. There is no aggression it, he is just used to meeting dogs and getting to pla with them i think. BEcause he is so large, people do not see this as the actions of an excited pup. Any thoughts for training a more polite greeting?

Ridiculous as it is(after owning/training so many dogs over the years!!), but I still don't see myself as anything of an expert but...when my girl went through this stage(around 6 months), she got to do the opposite of what she wanted.  She wanted to meet and greet and hopefully have a bit of a play but if she barked or jumped, I turned around immediately and walked away from the dog.  She would kind of be getting dragged behind, thinking "mum, you're going the wrong way.  Dog fun this way!!!".  I took her to a very dog heavy area and spent an afternoon doing this and she soon learned.  Now, she greets dogs nicely and quietly!
PS  Took more than one afternoon and I did need to keep up the dog meets for a few weeks till she got the message but now(10 months) she is no bother at all.

I have a friend that has an older dog who, although is nice, she is not adverse to teaching young whipersnappers some manners.  I 'accidently' bumped into her in the park with both our dogs off-lead and she taugh my girl under no uncertain terms, how to respectfully approach older/wiser canines!  Totally invaluable as my horror no longer bounds up to dogs but approaches slowly, reading the body signals.

Same as Cracar :-)  When I first had Tia I had to work initially on her on-lead aggression, but she wasn't just scared of dogs - her body language (and reading of it) was useless and she was very boisterous with dogs even in her old age, so her default reaction if off lead was to stalk over then thump them, and sometimes pin them, in an attempt toget them to play.  If they told her off, she had a go.

Once i'd worked on the less pleasant side of it, so she wasn't worried about them to start with, I did just what cracar did and it worked very nicely - she soon realised that being a tit got her further away :-P

I've also got a client doing it with her 6 month springador and it's working for him too - and he is proper bonkers!  Been badly told off a few times for rudeness.  I happened to bump into her last week at the park with 4 of mine, and it was a great practice session - the timing couldn't have been better, she was far enough away when we saw each other that her pup wasn't already going bonkers, and I got all my guys to sit and wait while she did the approach-and-retreat.  Once they reached us he was nice and calm :-)

Thanks guys, my problem is not with dogs that we get to meet, he is great then. It's the scenario of walking along the road and passing, or seeing up ahead, a stranger and a dog that you will not stopping to greet, and he will not be getting to play and sniff with. ideally he would get to say hello to them all but because of my breed people with small dogs (wrongly) want to avoid us so i'd prefer if they could avoid him being quiet and good...rather than lunging and barking and actually looking vicious not excited and happy to the uninitiated observer. He is great about meeting dogs that we get to stop and talk to thank god.

I would think this would work on this too.  What I mean is, you need to get some practise dogs to help you and stage encounters with dogs that he would ordinarily get to meet and greet only he is not allowed.  No canine interaction at all.  He needs to know that it is YOU that decides whether he gets to meet or not, not him or his doggy friends.  I would try this training with him for a while and although he is good with interaction with other dogs, it will always be on your terms.
Other than that, I think it's a maturity thing with him.  He's only a baby after all but that's the worse thing about Big dogs, everyone assumes they have the BIG brains too!!lol.  My girl gets treated like a big, bad dog when she's really got the nicest nature and silly, funny sense of humour.  He will grow out of his silly, bouncing behaviour and you will miss it.  I know I do when they become sensible dogs!

He's already growing too fast, just turned 6 months - overnight!!!!

That is my scenario Inka dogs on the other side of the road with my Safi (now 20 months).  I have worked on quiet with her, as ti was the shrieking that was the main issue, and i shorten the lead and praise calmness.

Now I can forestall by saying quiet, (no reaction from her) oh what a good girl, result in looking at me and being pleased with herself.

Works great if i spot the dog first, and if it is not a reactive sort that starts barking first!!!

At shows with loads of dogs, no great reaction at all.