I think so? I can't remember if it has its own separate one or shares with Maihama. I wasn't paying close attention when I exited Maihama so ended up just walking to the
Disneyland Hotel and after the first time, it was easy enough to keep doing it. I find I like to walk after I eat dinner.
I think the walk to Ikspiari is going to be closer to 15 minutes from MiraCosta because I don't think it has the nice walking path that Disneyland has. If you pull up Google Maps, you can get some idea of the walk by looking at Maihama Station. Though to be fair it is hard to estimate your walking speed since I don't know that much about you or your traveling party. I tend to walk a bit slower now because I am with my grade school daughter. I know we walked from entrance gates of Maihama Station to the hotel in 5-10 minutes. I know because I timed it for when we were checking out. The monorail path is Maihama/Ikspiari/resort gateway to Disneyland to Bayside (a station for good neighbor hotels) to Sea and back to the first station. So for us, since we were going the opposite direction as the monorail trying to get back to Maihama, it made sense to walk it. The walk between Disneyland and Sea is around 20 minutes but you need to walk back through Ikspiari because the walk to Bayside and around is much further because it's around the park.
For us it wasn't worth it to walk between the parks since the monorail ran often and was faster than the 20 minutes it would take us to walk.