We started using "baby sign time" at 19months (which is very similar to makaton), and which goes into the toddler years, there is a series of dvd's you can buy on e-bay or amazon (they are American, so only way I found to buy them) my son looooved them and immediately started copying what he saw and this is how i learned some basic signs. Despite being called "baby" sign time I think they can still be fun for older toddlers, and actually not babies - unless for the parents sake. Now we have extended this and use makaton which I have learned through his therapists and online. It is brilliant, can't recommend it enough. It enables them to have a means of basic communication while also encouraging their speech
I think makaton is more geared to those who may not need to use sign permanently, but use it in the short term and to aid speech...
Makaton (I think!) is also easier to learn as it directly relates to the action or word, you can aim at teaching yourself something like 5 signs a day and they would easily stick, as they make sense in the "sign" you attribute...
Maybe see if there are any local makaton courses being run locally?
So happy to hear some of you are using pec's, this is new to me and I find it a bit tricky introducing it
may need to start another thread to pick some brains....!