How can I travel outside the U.S. with a conditional Green Card?

You can take a brief international trip in Dec–Jan and re-enter the U.S. on your still valid 2 year green card that doesn’t expire until March 2026. That document alone is sufficient for airline boarding and CBP admission for a temporary trip abroad, so long as you return before it expires. The conservative practice, however, is to file the I-829 as early as your 90-day window opens and carry the I-829 receipt once it arrives The receipt automatically extends your status and green card validity 48 months beyond the card’s expiration while I-829 is pending.

You are allowed to travel once you have submitted your application for removal of conditions of residence. It is best to have the valid extension on you when you travel, to minimize potential issues at the time of re-entry. If you have someone who would be able to send you the original extension letter once it arrives that would be ideal if you cannot wait for the extension stateside.
The question regarding international travel requires an in depth consultation with an immigration lawyer. Feel free to reach out to me to set up an consultation at natalia@cohentuckerlaw.com

You can travel internationally using your card until the expiration date listed on it. After I-829 filing, you will receive and notice extending your conditional green card and will need to travel using that notice with the expired green card. Make sure to file your I-829 as soon as the filing window opens, so you can get your receipt notice before your conditional green card expires.