"We can come up by ourselves."

Translation: 我们可以自己上来。

[JustinCAquino]

可以 tends to be a question or asking permission. As a statement it is a translated differently. From the English to Chinese the phrase omits 可以, but from Chinese to English it will be phrased as a, "may". Like in English may 可以 and can 可能 are different.

[Revolutionnaire]

This sentence doesn't seem natural at all. I don't even know in which context it would be honestly.

[CinnamonTe1]

可以 can be used for permission or alternate possibilities.

The way I understand the Chinese, it could mean:

We can (have permission to) come up on our own.
(Might say this to a doorman, receptionist, or security)

We can (are able to) come up on our own.
(The listener doesn't need to come down and show them the way up)

That's my take, but it would be nice to hear from a native speaker.

[rianwardana]

我们可以一个人上来，为什么不对?? I remember on previous lesson that 一个人 is as same as 自己