Mi prima quería acampar allí arriba, pero yo preferí bajar al campamento antes de que anocheciera.

My cousin wanted to camp up there, but I preferred to go down to the campsite before nightfall.

Breakdown of Mi prima quería acampar allí arriba, pero yo preferí bajar al campamento antes de que anocheciera.

• yo: I
• querer: to want
• mi: my
• pero: but

Questions & Answers about Mi prima quería acampar allí arriba, pero yo preferí bajar al campamento antes de que anocheciera.

Why is quería used instead of quiso?

Quería is the imperfect of querer, and here it presents your cousin’s wish as a background intention or ongoing desire: she wanted to camp up there.

If you said quiso, that would be the preterite, which often sounds more like she wanted / she tried / she decided to, as a completed event. In this sentence, quería fits better because it sets up her preference in contrast to the speaker’s later decision.

So the contrast is:

• Mi prima quería... = my cousin wanted to...
• yo preferí... = I chose / preferred to...

This is a very common imperfect + preterite contrast in narration.

Why is preferí used instead of prefería?

Preferí is the preterite, so it shows a specific, completed choice in the past: I decided / I preferred to go down.

If you used prefería, it would sound more like a general or ongoing preference:

• preferí = I chose, at that moment
• prefería = I used to prefer / I was preferring / my preference was

In this sentence, the speaker is describing one concrete decision in a past situation, so preferí is the natural choice.

Why does the sentence include yo? Isn’t Spanish supposed to drop subject pronouns?