Maybe use Primal, but enable the caching service to be utilized for publishing? That way you're publishing to only one relay and not all of your relays? It's under settings, network.

If you’re on iOS, Nostur has low data mode. Damus has a setting to disable media previews. I haven’t heavily tested either one to compare data usage though.

Once personal proxy relays are a thing this problem will be greatly alleviated.

Your client connects to your one personal relay (which itself connects to other relays). Fewer connections from the edge device and greater flexibility re: caching and data transfer since your totally control the relay.

Also get IP cloaking for free if you host the relay outside your house.

You could reduce the amount of relays you’re using to just a few while you’re traveling. And who knows maybe you’ll realize you only need a few which is highly likely. Combine that with what nostr:npub1lrnvvs6z78s9yjqxxr38uyqkmn34lsaxznnqgd877j4z2qej3j5s09qnw5 said about disabling media previews.

nostr:npub10000000thpep7auj058803nqtymqlf3rw87lzhe6mkfeywnpxg5sjw7nql's relay proxy is probably the best solution, but lowering the number of relays you pull from helps.