In the Spanish pronunciation, this name sounds much nicer than one might think, though I shall not claim it to be the most beautiful in the Spanish language. Spanish vowels are very short and crisp, and do not glide into other sounds as they do in English, therefore, the last syllable does not actually sound like "gross".The intervocallic "g" is also different, it is the voiced variant of the "ch" in "Bach" when preceding "a", "o", or "u", or it sounds kind of like a softer variant of the "ch" when it is before "e", "i", or "y".
The pronunciation is "mee-lah-gros" and I think it's a sweet name because of that little princess, Milagros Cerrón, the second baby born with Mermaid Syndrome and survived.