18 month doctor appointment

Weight 30 lbs 12 oz, 94.5%
Height 35 7/8 in, 99.66%
Head 18 1/2 in, 27.9%

He's doing great! He's huge even though he's currently on the Adkins Diet, he's refusing to eat vegetables and fruit. His teeth look great, he's above average socially, and the doc was impressed that he's peeing on the potty at night. I'm concerned with his speech. He talks constantly, but I don't understand most of it and he's not using words he used to. He does have some new words though. Just not 20-50. So we are going to get evaluated for First Steps. Any thoughts on this?
I also asked the doctor his opinion on 2 year old preschool. His thoughts are that 2 year olds won't get as much out of it as 3 and 4 year olds, that's it mostly for socialization and that I might look into a playgroup or something like that once a week, which would be considerably cheaper.