Good Value in Caribbean but not exactly four-star
First, the highlights -- Secreto is stylistic, clean, private, scenic and quiet (or was when I was there a year ago). My elder sister loved the outdoor yoga they offered -- I mean a private instructor at your door? -- and the breakfast is very nice and so convenient -- it's like your own private kitchen. I also really liked the fact that with 9 rooms, it feels like your own retreat. I'd advocate the upper-level rooms -- ours was ground-floor, closest to reception and didn't have as nice a view as the upper floors.
For the less-than-highlights (I won't even call them low-lights) -- Please note it's true you can't swim at the beach outside the hotel. I didn't understand that from the web and was surprised. You do have to walk 5-10 minutes to a good beach but it's worth it. I only say that so you're not surprised. Also, the rooms are disinfected with a floral-spray that is at times overwhelming -- we had to unplug it -- too strong! Final pseudo-complaint is that it's in the middle of construction and/or empty lots -- it didn't feel like paradise only because you had to walk through abandoned sites en route. That was a year ago, and again, it may have changed since then.
Final note -- the resort is likely the best and most private on Isla Mujeres. But please know Isla Mujeres is not necessarily the most beautiful place in all of the Caribbean -- yes, it's nice and it's a very good value, but it's off the beaten path for a reason. It's not Cancun and it's not the Maya Riveria. For many, that's an appeal. What I didn't fully realize at the time, however, is that it cannot be expected to live up to resorts in other parts of the Caribbean that cost 3X as much (e.g. Turks and Caicos is more scenic but you pay for it!). What I did really, really like -- and what will likely bring me back again, is the walkable streets, the safe feeling (and reality) for two single women, the fun vibe and the accessibility from both Chicago and DC (direct flights). If you've got a lot more money to spend, if you're taking a once-in-a-lifetime-trip (perhaps from overseas), or if this is your first and likely only trip to the Caribbean or Mexico, I might consider other, more expensive all-inclusive resorts on the coast south of Cancun first -- then a few days on IM. But if you vacation often, are on a budget, have a relatively short timeframe (like we did), are looking for a safe, affordable, very pretty and super-fun place where you don't need a car, can bar-hop well into the wee-hours without worry, meet very nice locals, enjoy warm, turquoise water -- wait a minute, I think I've just talked myself out of all my reservations! --
Short story -- Secreto is nice. Please give it a try. But also recognize it's not the Ritz.