We can omit the subject of a sentence if it is obvious in the context.
A:
不如我哋今個星期六一齊食飯吖。 bat1 jyu4 ngo5 dei6 gam1 go3 sing1 kei4 luk6 jat1 cai4 sik6 faan6 aa1. Why don’t we have a meal together this Saturday?
B:
好呀。 hou2 aa3. Good. [= Sure.]
The subject 我哋 ngo5 dei6 can be omitted because Speaker A is obviously suggesting Speaker A and Speaker B do the activity 食飯 sik6 faan6 together.
A:
你有冇興趣今個星期六一齊食飯呀？ nei5 jau5 mou5 hing3 ceoi3 gam1 go3 sing1 kei4 luk6 jat1 cai4 sik6 faan6 aa3? Do you have an interest in having a meal together this Saturday? [= Are you interested in having a meal together this Saturday?]
B:
好呀。 hou2 aa3. Good. [= Sure.]
The subject 你 nei5 can be omitted because Speaker A is obviously asking if Speaker B is interested in the activity 食飯 sik6 faan6.
A:
你有冇時間今個星期六一齊食飯呀？ nei5 jau5 mou5 si4 gaan3 gam1 go3 sing1 kei4 luk6 jat1 cai4 sik6 faan6 aa3? Do you have time to have a meal together this Saturday? [= Are you free to have a meal together this Saturday?]
B:
好呀。 hou2 aa3. Good. [= Sure.]
The subject 你 nei5 can be omitted because Speaker A is obviously asking if Speaker B has time to do the activity 食飯 sik6 faan6.