As I've done, be sure your doctor gives you a letter stating the medicines you're taking, especially the injectable, so you won't have any problems with security and Customs. Airlines should put your meds in their ice box, but I would still bring some dry ice with you. Explain to customs that you must keep the meds cold. Put a buffer between the dry ice and meds, not directly on the dry ice. Have a nice trip...
Magnum
I discussed with my doctor delaying trt for nearly 6 months since I had a cluster of meetings, travel out of state, presentations, etc. He was perfectly fine with it and I'm glad I did it. As meakea mentioned, the additional logistics of keeping meds at the proper temperature, getting through security and customs, and dealing with the unknown side effects in a foreign country sounds challenging.
Discuss with your doc, but I'd go enjoy your trip, don't worry about the logistics and start when you get back. Good luck.
If it were me, I'd wait until after the trip. There are plenty of issues that can pop up while on treatment which would make being in a different country quite difficult. The logistics of carrying the meds with you at the proper temperature is also an issue. I'm not particularly a risk taker so those potential issues would make me wait until after the trip. If you're not easily rattled by the "what ifs", then maybe you're well-suited to start treatment now and deal with treatment while traveling.
As Jasmine suggested, please talk to your doc and get his opinion.
I would speak with your doctor. I am avoiding traveling outside the country while on treatment. I do not want to risk being in a foreign country and having a serious side effect or damaging or losing my meds If I had a trip, and it was safe to wait to start treatment, I would, in fact I did. Language could also be an issue, even for just over the counter meds.
Other things to consider, now that i am on treatment I am not sure I could handle flying for too many hours and traveling through airports some days. I would definitely not have as much fun while on treatment. Not enough energy and feeling like I have the flu is not great for a vacation. Treatment makes you more susceptible to infections too I hear.
Love to travel but have put further ideas for trips this year on hold until i am done. Best of luck and hope you enjoy your trip.