Waiting for My Biometric Appointment, Should I Travel

We just filled the form I-751 to remove my conditional residence ( I had a conditional residence because we applied before 1 yr being married)
About 3 weeks ago I received a letter saying that they received my application form ...
"Your conditional resident status is extended for a period of 1 yr, During the 1 yr extension you ARE authorized for employment & travel. ( This extension and authorization for employment & travel does not apply to you if your conditional resident status has been terminated)

In order to further process your petition, you will be receiving an application supper center (ASC) appointment notice with the specific time , date and location to capture your fingerprints, photo, signature. You MUST wait for your appointment notice before going to the ASC for biometric processing. "

I'm wondering how soon will I receive the letter for the biometrical ?
I'm planning a trip by the end of March, outside of the US (South America) and I was wondering if I can go BEFORE taking my biometrics?
In the letter says that I can travel, but I'm wondering what will happen if during my trip I receive the letter with the appointment for my biometrics & I loss it? what would happen? can I request a new appointment?
Will I have any issue to come back ?

The receipt date on this letter is : 02/07/2011
How long does it usually takes until the appointment for the biometrics?

There will be a person checking my mail, I was thinking that if I receive the letter while I'm outside of the country, I could call to change the date? can that be done?

by the way I'm in Texas.

Thanks in advance! :)

I would expect you to receive notice soon. Within the next few weeks.

What do you mean by "loss it" - do you mean that you expect the person who is checking your mail to be careless and to lose your mail, or do you mean that you might have to reschedule because you're planning an extended trip and thus might not be back in the U.S. by the time of your appointment? Instructions for requesting an adjournment are on the notice form - obviously an adjournment can delay the resolution of your case. You will want to request an adjournment in a timely manner in advance of the scheduled hearing date.