The sentence We talked until late seems grammatical to me.
I find 39 hits for until late followed by a period in the Corpus of Contemporary American English (450 million words). 24 are in fiction writings. Here are the first 20 hits for fiction.
1 N'T BE BACK UNTIL LATE . 3
2 N'T BE IN UNTIL LATE . 2
3 N'T BE HOME UNTIL LATE . 1
4 WOULD NOT BE UNTIL LATE . 1
5 WORK TO DO UNTIL LATE . 1
6 TO GET AWAY UNTIL LATE . 1
7 THEM WITH QUESTIONS UNTIL LATE . 1
8 STUDIED ALONE , UNTIL LATE . 1
9 STOPS COMING HOME UNTIL LATE . 1
10 PLOT AGAINST ME UNTIL LATE . 1
11 NOT COME HOME UNTIL LATE . 1
12 NOT BE HOME UNTIL LATE . 1
13 N'T GET DARK UNTIL LATE . 1
14 N'T COME BACK UNTIL LATE . 1
15 FROM THE LODGE UNTIL LATE . 1
16 DID N'T LEAVE UNTIL LATE . 1
17 CARDS OR BACK-GAMMON UNTIL LATE . 1
18 AT THEIR OFFICE UNTIL LATE . 1
19 AT MUG SHOTS UNTIL LATE . 1
20 'LL BE GONE UNTIL LATE . 1
Here's an example with context:
Evenings he goes into the bedroom and shuts the door, comes out
occasionally for soup or cheese. Finally he starts going to a coffee
shop after he gets home, and then he stops coming home until late .
She'll go to sleep after the news, and when she wakes up for work he's
snoring on the other side of the bed.