Steve I think the difference between curly and straight quotation marks is the font being used. They appear differently in different fonts, the most common fonts being Times New Roman (curly) and Arial (straight), and the word processing program being used might also affect quotation appearances. The use of quotation marks annoys me when there is a word or phrase being written about but it’s not an actual ‘quote.’ From my understanding, if a word or phrase is being discussed, such as whether ‘Mountaineer’s Route’ or ‘Mountaineers’ Route’ is more proper, it is in single, inverted commas, distinguishing it from an actual quote from a cited source. “Many people type ‘Mountaineers Route’ out of ignorance.” – bobpickering < this would be correct usage, but I know the rules vary in different English speaking countries.
As for Sierra vs. Sierras, I prefer Sierras since it’s not only Americanized already like many other Spanish words, but its pluralization sounds more descriptive of the vast range. For example, “Wow, look at the Sierra today!” and translated to English, “Wow, look at the mountain range today!” both sound really general and broad. “Wow, look at the Sierras today!” encourages seeing the mountains (plural) with more individuality instead of as just one big range. Just my thoughts.
