My 60 day window was earlier this week. I started logging in via the website after 7am EST.. (so an hour later than reservation openings), and Space 220 was available all 8 days of my trip and all at "normal" dinner times. I adjusted my bookings throughout the course of the day/evening and Space 220 was available (less available, but still available all days). I made some more changes the next day or two, still had Space 220 on *most* but not *all* days... by day 5 after my window opened, I no longer saw availability. The point being, unless you are going peak season, trying to book peak day... don't stress... just log in the morning of your 60-day window and you'll have plenty to choose from.
And i can confirm that choosing "breakfast, lunch, dinner" returns poor results.. pick an hour kinda in the middle of when you'd like to eat, and you will see availability (they check in 3 hour blocks... so, if you put in 6pm, they check 5-7pm, I think)... they def. return a range... then just keep bumping you "requested" hour in or out around the range they provide - it's noted on the screen presented.
Also - since my window just opened, I'm going to be there mid-Janauary, a typical "slow" time - BUT I had availability for all the current "hard to get" up through about day 3-4 post window (BOG, CRT, Space 220, Olgas, SciFi, MK Fireworks parties, etc)... YRMV based on the season demand you are planning for.