It seems most people think the correct spelling has only one L (Ilinza), but an official IGM map in Ecuador spells it with two L's. Paul, in the final entry below, notes that he has both spellings in his various guide books... so it's not 100% either way!
Bob Ayers: In Quito, the guide services pronounce it with an el sound, like the english "eel-ee-knee-za". I assume you know that the Spanish "LL" sounds much different from "L". [In fact when I think about it, the combo "I-LL-I" would be a mind-bender to pronounce!]
Nathan Trinklein: I've climbed the north summit, and on the topo map I purchased from the IGM in Ecuador it's spelled "Illiniza". Good luck finding a consensus...
Jeff Grant: According to the "Lonely Plan guide to Ecuador" and to "Ecuador: A Climbing Guide", it's one 'L'.
Richard Ferguson: The book "Climbing and hiking in Eucador" says Iliniza, one L. I don't think that I have a government issued map, which I think would be the most authoritative source.
Arun Mahajan: The book, 'Equador, A Climbing Guide' by Yossi Brain (pub: The Mountaineers, 2000 edition), calls them the Ilinizas, Sur and Norte, with one 'L'.
Rodney Ley: I'm looking at a poster of Iliniza Sur that I bought in Ecuador. Based on that documentation I'd say "One L".
Roy Lambertson: I vote for one "L," based on the pronunciation. "L" as in "Lima" rather than "LL" as in "caballero." Remember, in Spanish, you pronounce every letter... except the ones you don't. A memorable climb; I went up Iliniza Norte in 1990 as a marathon day hike from near the Panamerican Highway. I shredded my cheap Otovalo wool gloves on rock near the top, searching for the true summit in dense fog. At the rime-encrusted summit the clouds cleared for a few seconds and I could see Cotopaxi, across the central valley, as well as other Andean peaks hundreds of miles away. Then the fog closed in again. Trying to hitch-hike back to Quito late that evening was an adventure also as I recall.
Steve Bonowski: For what it's worth, I have one of the maybe rare copies of Michael Koerner's "The Fool's Climbing Guide to Ecuador & Peru", self-published in 1976. He uses only one "L" for the Ilinizas. As a humorous side, the book is totally on Ecuador. What he says about Peru, on one page: "Peru, they tell me, has some excellent climbing..........."
Aaron Schuman: Iliniza should have one 'L' only. Llike llama:
A one-elled lama's a priest, A two-elled llama's a beast, And I'll bet you my woolen pajamas, There aren't any three-elled lllamas.
Paul Wilson: Only one book I have uses two L's, all the rest (many) show it name with one L.