I think my experience with dairy was very different! I got there at 3am every day and left at 11am, after all the milking, feeding etc had been done. Basically, take warm clothes for dairy as you will get cold, no matter what time of year it is. I wore thermal leggings, a thermal base layer, thin fleece, thick fleece and waterproofs (but I went in January when it was snowing like hell so that makes a difference!). I got left alone to do the milking while the head dairyman went to go and take his daughter to hospital, once...LA can be very unpredictable so you just have to be prepared for anything.
For lambing, again, literally be prepared to do anything. Don't bulk up too much because you'll be running around chasing things, but at the same time make sure you're wearing layers to take off and waterproof trousers as a minimum. Also, make sure your sleeves will roll up easily. During my lambing placements, I was on my feet every second of the day, moving sheep, moving lambs, moving bedding, tagging lambs, pulling lambs out, giving injections, replacing hay and water...the list goes on and on!
Obviously me and nerdcake will have had different experiences while out on LA experience - I was on a massive commercial farm which churned out milk and lambs, whereas nerdcake sounds like they were on a smaller farm, but both experiences are valid and useful.