CA newbie questions

2 days for Disneyland and 1 for DCA is good. DL has far more rides than DCA. Depending on when you're there, DL has 2 nighttime shows, fireworks and Fantasmic, while DCA only has World of Color. Park hopping is better - it really is just a hop between the two. That way if rides you want to do break down you can do them another day. As far as walking, DL would be a similar amount to Magic Kingdom, and DCA to Studios. I don't know anything about using ECVs but I do see people renting them from Disney.

We just went for three days and that was perfect - we even wrapped up a bit early on the third day. I would suggest getting the park hopper - especially on the DCA day you may find you've done everything you wanted to do, and park hopping is super easy.

3 days is perfect. Parkhopping is worth considering as parks are so close compared to WDW. Also without kids, maybe consider splurging on the Premier pass for one of the days. Can avoid rope drop and go oldschool without having to manage your day through the phone (so good). Want to go on the ride you want when you want. Wife and I done a day with the pass earlier this year it was one of the most relaxing park days ever. Well worth it.

I agree, 3 days is good and I would get a park hopper. I actually find that I do more steps at DLR as opposed to WDW because it's so easy to keep hopping back and forth between the parks. Also if you are staying at a hotel within walking distance, that will add to your steps.

ECVs are pretty common, I don't know anything about where is best to get them though.