You will become a US citizen only after you take the oath of Allegiance and until then you will be a permanent resident. Even if you are done with your naturalization interview, you will only be a permanent resident until your receive your naturalization certificate. Hence, you can travel abroad as a Green Card holder, while your US citizenship application is pending.
However, you need to remember few things while you plan to travel abroad, while Form N-400, Naturalization Application is pending and you must fulfill the continuous residence and the physical presence requirement and your trip must not be lengthy. At the same time, if you have not registered for updates by emails or text messages, you will have to ask your friend or your relative in the United States, to check your mails and inform you about your biometrics appointment and about your interview. You will have to see to that you do not miss these appointments and missing your interview or your biometrics appointment will delay your case.
Nevertheless, it is better to travel abroad after you submit biometric information. Some service centers accept walk-ins and if your USCIS service center accepts walk-ins, you can visit the application support center at any time and submit fingerprints and then travel abroad. Until you take the oath of allegiance, you can travel abroad as a Green Card holder and return to the United States with your valid Green Card. Remember that, you will have to surrender your Green Card only at the time of taking the oath and you will not lose your Green Card until then.
However, it is wise to remain in the United States during the naturalization process. But if you are required to travel abroad due to a genuine reason, you may do so, but remember to get back to the United States for your naturalization interview and to get your fingerprints taken. Similarly, the number of days that you remain abroad will be counted and see to that your trip will not affect your continuous residence.