Definitely need to get some backups there... If you're aiming for top 20, definitely pick and choose at least 2 backup schools from the top 50, that would would feel comfortable going. The things I considered when choosing my backups was: city, overall school strength (will it offset their lower reputation in ECE?), and individual stars within the faculty. Don't take anything for granted though... I did that, and got rejected from what I would have thought as "safe" schools. This year and the next are not the most ideal times to be applying for grad school (or jobs, for that matter).
My experience this year has been that I heard back positively only from the schools I had a good feeling about my potential advisor. So what does this mean? I looked at how active the profs were, how many students they had (very hard to tell, lots of googling here), and what grants they've been getting lately (that will ultimately define your work with your advisor).
Whatever you do, don't apply to a school just to have applied... you'll be almost guaranteed to not get in. Determine your priorities, and then sift through the schools to pick and choose <10 schools (anything more, and you'll be preparing applications 40 hrs a week for a month -- my two cents).
I hope that helps!