You can use either dofollow or nofollow, nofollow links will also count in the your backlinks. But it is better to post your travel blogs on dofollow blogs if you didn't get it don't hesitate to use blogs with nofollow links.
Instead of creating backlinks, think of getting targeted traffic. Imagine if you have dofollow blog related to travel, and all people visit there is people who owns travel websites and want to put links on them? What good will it do then?
Write quality articles and submit them to directories. It helps.
you can try to search it manually but first install seoquake to see the page rank of the blog you were visiting and also do follow indicator tools to know if the page you were visiting is do follow or not.
There are also some authority websites that weight a lot when getting a link from there, even though they are no-follow. You know, do-follow is not the Holly Graal.
No body could give me a right answer! It seems to be hard to find dofollow travel blogs or dofollow travel forums! I have been looking for a long time but I just found nofollow ones!
Google it and find few do follow blogs or forums there are several applications available on net which lets you know which one is do follow n which isn't.