To thine own self be true. Right?
Seriously, if you're negotiating a marriage, and essentially everything that comes before the wedding is a sort of negotiation, you should honestly and openly discuss your needs and desires with your woman.
Honesty will almost never bite you in the ass, but deceit certainly will.
The worst that can happen if you're honest with your wife-to-be (or even your current wife) is that she'll tell you that your plans are unacceptable to her. She may choose not to go through with the wedding, but if already married she will most probably want to discuss the matter before taking rash action (i.e. messy divorce).
OTOH, if you lie to her, you're screwed on two counts. First of all is the infidelity, but the larger issue for her will be that you lied. If she can't trust you, your relationship is over.
I don't think Mrs. Ciego is all that different from most other women. She is a conservative Catholic, not terribly sexual, and while she doesn't necessarily "like" what I do in C.R., at least she never has to worry that I'm lying to her. As the cards are on the table, she can make choices, and so far she has chosen to treat my trips to C.R. as adventures. She understands that at the end of the day, she and I will still share the same life, same table, same bed and most of the same golas for living.
If you start a relationship with the intention of being dishonest, I urge you to rethink that idea.
BTW, all that being said: If you're going to lie, please do it well. Take two days of tourism outside the Gulch, bring four different, different-colored shirts so the one or two days outside the Gulch will appear to be several days instead, in terms of photographic evidence. Do not return home with chica phone numbers on scraps of paper in your pocket.
Recently, a CRT brother was busted because his wife found a hotel receipt he had forgotten to discreetly file away. Little clues count; avoid leaving them.
* Route your cellular VMB to a stateside number, then use Skype, Magic Jack or another phone service to check your messages. Do not use your U.S.A.-based GSM phone to call the states, lest your spouse get a peek at your phone bill.
* If your stated purpose for travel to C.R. is to study Spanish...study Spanish, and have the study materials casually available to your spouse.
* Do not inadvertently speak Spanish during sex.
Still, I really believe that honesty remains the best policy. If your wife cannot or will not understand and accept your needs, I submit that you married the wrong woman. JMHO.