As a self proclaimed semi-professional MiraCosta booker (I made several "practice" bookings, tried getting through almost nightly for about 2 months, and finally booked Harbor View Alcove rooms for three consecutive nights in late May) I feel obligated to chime in. BTW if you think doing all this is nuts you should see the embarrassingly elaborate spreadsheet I've created for this trip.
MiraCosta Rooms become available at 11am Japan time for rooms 5 months out. Japan does not have daylight savings so right now they are 13 hours ahead of east coast time so you need to be ready at 10pm on the east coast and 7 pm on the west coast. You can only book one night at a time for harbor view rooms and above; other rooms you can get I think up to 5 consecutive nights. If you book one night at a time you need to make sure you book the exact same room type each night or you'll have to change rooms. You will be charged 30k yen each night. This is refundable - I made and cancelled reservations a couple times and it worked fine. The deposit was charged and refunded in the same day. I used a Citi MasterCard and it worked every time and I didn't tell Citi in advance. I highly recommend making a trial reservation. I learned a lot. For example your card will go through a weird approval screen I've never seen on another site before and if you're not expecting it you might screw something up.
Things I learned through practice: refreshing your browser when the clock turns 10 will not work fast enough every time. A practically fool proof way of getting through in the first few seconds while every room type is available is to bookmark the URL for the night you need. I went to a day that was available, chose my room type and whatnot, then in the URL box I changed the date to the date I needed and hit enter. Then I bookmarked that URL. At 10pm 5 months ahead of my dates I clicked on that bookmark and boom, all room types available, including concierge level. I did this three nights in a row and it worked out great.
Another thing - every night about 30-35 minutes after rooms became available another set of rooms would be freed up. Every single night. I could have booked harbor view rooms at 9:30 (this was before DST kicked in) virtually every night I tried. Not sure if this is from people's cards rejecting or what but it happens every night.
So that's my 2 cents. Any questions I'd be happy to answer!