Can competent brass players play large leaps?
Yes. Remember that brass instruments in their fundamental form can play only tones that are found in the overtone series. Large leaps are inherent in the nature of brass instruments, especially in their lower registers.
In the upper register, because the overtones are closer together, playing a note accurately is more dependent on the player's control: breath pressure, lip tension, and indeed ear. Here I answer "yes" because the question specifies "competent," but remember that it is unusual to attend a symphonic performance, even a professional one, without hearing a flubbed note from the horns.
Look at a few horn parts from the late 18th through the late 19th century. They don't just contain leaps, their characteristic style is based on leaps. This music is an important part of the horn repertoire. For a horn player, a few fourths, sixths, or octaves are like breathing.
You'll also want to look at idiomatic writing for the modern valved horn, of course, in more recent works, where you'll find leaps both in passages that evoke the classical brass idiom (Fanfare for the Common Man comes to mind) and in passages that are mostly stepwise, as with melodies written for any chromatic instrument.
In general, as an orchestrator, you will want to become more familiar with all of the instruments of the orchestra. Buy a cheap used horn, or borrow one. Learn to play it, even badly. This will give you more insight into the answer to this question than any of us can. Look at a book of orchestral excerpts that a student hornist would use. Listen to professional recordings of these pieces. Look for videos online of students playing these pieces, too: this will give you a sense of what's hard and what isn't.
While you're doing all of that, you're bound to come upon passages that are similar to the one you're writing, to serve as a model. How do other composers handle the sort of texture you want to create (for example, the part crossing in the last measure is unusual).
Finally, make friends with a horn player. Don't just ask them to look at the part but ask them to play it for you, so you can hear whether it actually sounds as you imagine it does. They'll tell you if anything doesn't make sense or if you need to be careful about anything.