employee's canteenやstaff canteenで「社員食堂」という意味になりますが、同じ同僚の方に話しかけているのであれば、employee'sは文脈上分かるので省略可能で、Let's have lunch at the canteen.で十分です。「一緒に〜しよう」はおなじみ、Let's doを使います。
▪Cafeteria
a restaurant in which customers serve themselves from a counter and pay before eating
Other names:
a.Lunchroom
b.Snack bar
c.Lunch counter
Examples
a. Hey, we can grab lunch at the Lunchroom
b. Hey, we can grab lunch at the Snack bar
▪Cafeteria
食事をする前に払うレストラン、食堂
他の呼び方:
a.Lunchroom
b.Snack bar
c.Lunch counter
（英文）
a. Hey, we can grab lunch at the Lunchroom
b. Hey, we can grab lunch at the Snack bar
（訳）
a. Lunchroomでお昼ご飯をたべよう。
b. Snack barでお昼ご飯をたべよう。
A cafeteria/lunchroom is a dining area at an office building, where meals may be purchased and eaten. Therefore when you make this suggestion you can also suggest how people can pay for the meals. The company may pay for it or the amount can be deducted from the employee's salary.
---> A canteen is a place in a factory, shop, or college where meals are served to the people who work or study there.
---> A cafeteria is a restaurant where you choose your food from a counter and take it to your table after paying for it. Cafeterias are usually found in public buildings such as hospitals and stores.
Rennie had eaten his lunch in the canteen.
You can't eat this food in the cafeteria.
---> "canteen"とは、工場やお店、大学などそこで働く人や学生のための食堂の事です。
---> "cafeteria"とは食堂のことで、食べ物を選びカウンターへもっていき、そこでお金を払い、テーブルへ自分で持っていく場所の事を言います。
"Cafeterias"は、病院やお店などの公共の場所で見かけることが出来ます。
例
Rennie had eaten his lunch in the canteen.
（レニーは食堂で昼食を食べました）
You can't eat this food in the cafeteria.
（食堂でこの食べ物は食べることはできません）
The traditional name for a place where the food is served and people sit down to eat, is 'canteen.' However as fashions change and a wider selection of food and snacks becomes available, there is a move towards the use of 'cafeteria' in places like schools and factories. Another way of describing this area may be a dining room or dining hall, if this area is specifically for the purpose of dining.
Let's eat at the company canteen for a change...I hear the food is excellent!
Many larger companies provide a canteen or cafeteria for their employees...
The food quality may vary from country to country... but in Japan it's rather good!
"Let's eat at the company canteen for a change...I hear the food is excellent!"
多くの大企業が、従業員のために食堂を設けています。
国によって食べ物の質は異なりますが、日本はかなりいいです！
"Let's eat at the company canteen for a change...I hear the food is excellent!"
たまには社員食堂で食べよう。料理がすごくおいしいと聞いたよ。
The most common definition of the public place where you can eat that is normally provided by the company, such as a hospital, a business would be called a, "cafeteria." We can also use the term, "lunchroom," as this simply refers to a public place that sells food and has places to sit to enjoy your lunch.
日本 
南アフリカ 
イギリス 
アメリカ合衆国 
