For clean blue sky vistas Museum Hill is a pretty good location, particularly the large, flat plaza between the International Folk Art Museum and the Museum of Indian Culture. Mountains, adobe structures, flowers, it has it all. In the Summer you are just about guaranteed to have nice cumulus build-ups over the nearby mountains. And it's all very clean, kempt, and thoroughly sano. And there's plenty of free parking. And you can have a reasonably good lunch at the little cafe there which is generally not too crowded. Only downside is that most of the best views are southward, so you may need some flash fill.
Will let the locals make other suggestions. I'm tempted to mention the Cathedral, but it's in a tight, crowded area where it might be hard to cobble a wedding party into a good shot. And of course there are adobe porticoes galore. Santa Fe is a curious town for a photographer. It's all about details and close-in perspectives, but there are few distant or expansive views.